v25.4 initial paths/files, and template fixes for supporting them pre-alpha-release (#20199)

* Support pre-testing-release phase, where we have versioned docs and a `versions.csv` entry, but not yet any releases.yml entry, for the new major version.

- Release info plugin: Add support for having versioned docs and versions.csv entry without any releases.yml entries.
    Previously this would yield a `NoMethodError` and block the build
- Version switcher: Filter dropdowns to only show versions that have releases (testing or prod) in releases.yml
  - Prevents "No releases available" from appearing in the menu across versions, during this pre-alpha state.

These changes ensure that we can merge and preview docs for the forthcoming version before it has reached alpha,
while leaving it hidden from public view, only accessible via direct /<version> URLs. Note that the /dev alias will not work
until we set the new version as `dev` in _config_cockroachdb.yml upon the first alpha release.

* Add data validation to release_info Jekyll plugin

- Validate all release dates before processing to prevent Date.parse crashes
- Validate required docker configuration exists before accessing nested hash
- Fail fast with descriptive error messages instead of silent data corruption
- Error messages include release name and major version for easy debugging

Addresses build stability concerns while ensuring data quality by catching
malformed entries in releases.yml during build time rather than at runtime.

Fixes potential crashes from:
- nil/empty/invalid release_date values
- missing docker.docker_image configuration

* Add initial paths and files for v25.4

* Temporarily use prior release branch for SQL diagrams

Author: mikeCRL

src/current/_data/v25.4/cluster-settings.csv

@@ -0,0 +1,133 @@
+- metric_id: seconds.until.enterprise.license.expiry
+  description: Seconds until enterprise license expiry (0 if no license present or running without enterprise features)
+  y-axis label: License Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.ca
+  labeled_name: 'security.certificate.expiration{certificate_type=ca}'
+  description: Expiration for the CA certificate. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.client-ca
+  labeled_name: 'security.certificate.expiration{certificate_type=client-ca}'
+  description: Expiration for the client CA certificate. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.client
+  labeled_name: 'security.certificate.expiration{certificate_type=client}'
+  description: Minimum expiration for client certificates, labeled by SQL user. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.ui-ca
+  labeled_name: 'security.certificate.expiration{certificate_type=ui-ca}'
+  description: Expiration for the UI CA certificate. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.node
+  labeled_name: 'security.certificate.expiration{certificate_type=node}'
+  description: Expiration for the node certificate. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.node-client
+  labeled_name: 'security.certificate.expiration{certificate_type=node-client}'
+  description: Expiration for the node's client certificate. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.ui
+  labeled_name: 'security.certificate.expiration{certificate_type=ui}'
+  description: Expiration for the UI certificate. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.ca-client-tenant
+  labeled_name: 'security.certificate.expiration{certificate_type=ca-client-tenant}'
+  description: Expiration for the Tenant Client CA certificate. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.expiration.client-tenant
+  labeled_name: 'security.certificate.expiration{certificate_type=client-tenant}'
+  description: Expiration for the Tenant Client certificate. 0 means no certificate or error.
+  y-axis label: Certificate Expiration
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+  essential: true
+- metric_id: security.certificate.ttl.ca
+  description: Seconds till expiration for the CA certificate. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+- metric_id: security.certificate.ttl.client-ca
+  description: Seconds till expiration for the client CA certificate. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+- metric_id: security.certificate.ttl.client
+  description: Seconds till expiration for the client certificates, labeled by SQL user. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+- metric_id: security.certificate.ttl.ui-ca
+  description: Seconds till expiration for the UI CA certificate. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+- metric_id: security.certificate.ttl.node
+  description: Seconds till expiration for the node certificate. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+- metric_id: security.certificate.ttl.node-client
+  description: Seconds till expiration for the node's client certificate. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+- metric_id: security.certificate.ttl.ui
+  description: Seconds till expiration for the UI certificate. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+- metric_id: security.certificate.ttl.ca-client-tenant
+  description: Seconds till expiration for the Tenant Client CA certificate. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.
+- metric_id: security.certificate.ttl.client-tenant
+  description: Seconds till expiration for the Tenant Client certificate. 0 means expired, no certificate or error.
+  y-axis label: Certificate TTL
+  type: GAUGE
+  unit: TIMESTAMP_SEC
+  how_to_use: See Description.