feat(registry): add raw registry versions dump to JSON

[sasa-tomic]

Motivation

• Enable exporting registry history as JSON for precise diffs.

Solution

• Adds --dump-versions to dre registry.
• Introduces direct reading of local registry pb files, decode records, and emitting a flat JSON array of {version, key, value}. The existing registry API was not sufficient for this requirement since it (ic_registry_local_registry::LocalRegistry, FakeRegistryClient, etc.) provides snapshots at a version (latest or specified) and key-family APIs, but not "list mutations per version" like the .pb changelog files store does. So it was necessary to read the raw .pb files directly.
• Supports Python-style negative indices for ranges and base64-encodes unknown bytes; decodes common protobuf records when possible. This allows queries like: give me the last 5 records --dump-versions -5 or give me the first 5 records --dump-versions 0 5

Details

• Looks up local_registry dirs under dre-store/local_registry for current network; honors DRE_LOCAL_REGISTRY_DIR_OVERRIDE for tests.
• New unit tests under rs/cli/src/unit_tests/registry_versions.rs validating per-version dumps and range.

Meta

Example usage to get the last 5 registry versions (changes):

❯ dre registry --dump-versions -5
 2025-10-20T11:27:03.436Z INFO  dre > Running version 0.6.7-a012c0f9
 2025-10-20T11:27:03.460Z INFO  dre::store > Using local registry path for network mainnet: /home/sat/.cache/dre-store/local_registry/mainnet
[
  {
    "version": 54100,
    "key": "blessed_replica_versions",
    "value": {
      "blessed_version_ids": [
        "45657852c1eca6728ff313808db29b47c862ad13",
        "285897dae3a2cb60c50d9d8dd7327f18c3c372b9",
        "286295f0397521cd59ca7792df446c57379204fa"
      ]
    }
  },
  {
    "version": 54100,
    "key": "replica_version_206b61a8616bc93d36d6a014e5cc8edf1ba256ae",
    "value": null
  },
[...]

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