Add x-glean-deprecated to Speakeasy deprecation format transformation

[travis-hoover-glean]

Summary

• Add transformGleanDeprecated function to convert x-glean-deprecated annotations to Speakeasy-compatible deprecation format
• Integrate the transformation into the main spec processing pipeline
• Add comprehensive tests for the new transformation

Details

This PR enables Speakeasy SDK generation to properly handle deprecated API elements by transforming Glean's internal deprecation annotations to the format Speakeasy expects.

Transformation Logic

For each element with x-glean-deprecated, the transformer:

1. Adds deprecated: true (standard OpenAPI field)
2. Generates x-speakeasy-deprecation-message with the format:
   "Deprecated on {introduced}, removal scheduled for {removal}: {message}"
3. Preserves the original x-glean-deprecated annotation for internal tooling

Example

Input:

paths:
  /test:
    get:
      x-glean-deprecated:
        id: "uuid-123"
        message: "Use /v2/test instead"
        introduced: "2024-01-15"
        removal: "2024-07-15"

Output:

paths:
  /test:
    get:
      deprecated: true
      x-speakeasy-deprecation-message: "Deprecated on 2024-01-15, removal scheduled for 2024-07-15: Use /v2/test instead"
      x-glean-deprecated:
        id: "uuid-123"
        message: "Use /v2/test instead"
        introduced: "2024-01-15"
        removal: "2024-07-15"

Supported Deprecation Targets

The transformation handles x-glean-deprecated on:

• Operations (path methods)
• Parameters
• Schema properties
• Nested structures (e.g., request body schemas)

Test plan

• Added unit tests for operation-level deprecations
• Added unit tests for parameter-level deprecations
• Added unit tests for schema property deprecations
• Added unit tests for nested deprecations
• Added unit tests for specs without deprecations (no-op case)
• All 44 tests pass