[exporter/exporterhelper] Migrate TimeoutConfig to schema-based configuration generated by mdatagen. (#15505)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

Migrate `TimeoutConfig` (part of exporterhelper) to mdatagen
schema-based configuration. Removes the hand-written TimeoutConfig
struct and NewTimeoutConfig constructor in favor of generated code
driven by metadata.yaml and config.schema.json.

<!--Authorship attestation. See AGENTS.md for details. AI agents must
not check this box on behalf
of the user; the human author must check it themselves before the PR is
ready for review.-->
#### Authorship

- [x] I, a human, wrote this pull request description myself.

<!--Please delete paragraphs that you did not use before submitting.-->

Author: jkoronaAtCisco

.chloggen/migrate_timeout_config.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/otlp)
+component: pkg/exporterhelper
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Migrate `TimeoutConfig` to schema-based configuration generated by mdatagen.
+
+# One or more tracking issues or pull requests related to the change
+issues: [15505]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

exporter/exporterhelper/config.schema.json

@@ -0,0 +1,20 @@
+{
+  "$id": "go.opentelemetry.io/collector/exporter/exporterhelper",
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$defs": {
+    "timeout_config": {
+      "type": "object",
+      "properties": {
+        "timeout": {
+          "type": "string",
+          "description": "Defines the timeout for every attempt to send data to the backend. A zero timeout means no timeout.",
+          "default": "5s",
+          "minimum": 0,
+          "pattern": "^([0-9]+(\\.[0-9]+)?(ns|us|µs|ms|s|m|h))+$"
+        }
+      },
+      "description": "A timeout configuration. The timeout applies to individual attempts to send data to the backend."
+    }
+  },
+  "title": "pkg/exporterhelper"
+}

exporter/exporterhelper/generated_config.go

@@ -0,0 +1,20 @@
+{
+  "$id": "go.opentelemetry.io/collector/exporter/exporterhelper/internal",
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$defs": {
+    "timeout_config": {
+      "type": "object",
+      "properties": {
+        "timeout": {
+          "type": "string",
+          "description": "Defines the timeout for every attempt to send data to the backend. A zero timeout means no timeout.",
+          "default": "5s",
+          "minimum": 0,
+          "pattern": "^([0-9]+(\\.[0-9]+)?(ns|us|µs|ms|s|m|h))+$"
+        }
+      },
+      "description": "A timeout configuration. The timeout applies to individual attempts to send data to the backend."
+    }
+  },
+  "title": "exporterhelper/timeout"
+}

exporter/exporterhelper/generated_config_test.go

@@ -0,0 +1,6 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate mdatagen metadata.yaml
+
+package internal // import "go.opentelemetry.io/collector/exporter/exporterhelper/internal"

exporter/exporterhelper/internal/config.schema.json

@@ -0,0 +1,13 @@
+type: exporterhelper/timeout
+parent: pkg/exporterhelper
+
+exported_configs:
+  timeout_config:
+    description: A timeout configuration. The timeout applies to individual attempts to send data to the backend.
+    type: object
+    properties:
+      timeout:
+        description: Defines the timeout for every attempt to send data to the backend. A zero timeout means no timeout.
+        type: duration
+        default: 5s
+        minimum: 0