refactor(ci): remove unused split-repository logic from release notes generator

[jinseopkim0]

Removes split-repository release notes parsing and URL linking logic from the BOM release notes compiler tool (ReleaseNoteGeneration.java).

Since all major Java client libraries (bigtable, firestore, pubsub, pubsublite) have been migrated into the monorepo, their release tags are hosted on googleapis/google-cloud-java and their old split repositories are no longer used for new releases. This change cleans up all associated dead code.

Verifications:

• Completed local compilation, tests, and formatting successfully (ReleaseNoteGenerationTest passed).

[gemini-code-assist]

Code Review

This pull request removes the split-repository logic from the release note generation tool, simplifying the code to only support the monorepo. The review feedback points out that after these changes, some variables inside the loop in reportClientLibraryVersionDifference are now unused and can be removed. Additionally, the releaseUrl calculation can be hoisted out of the loop to avoid redundant calls and object allocations.

[jinseopkim0]

/gemini-review

[jinseopkim0]

/gemini review

[gemini-code-assist]

Code Review

This pull request simplifies the release note generation by removing support for split repositories, consolidating the release URL generation to use only the monorepo URL format, and cleaning up unused imports and methods. A review comment suggests using Guava's ImmutableList.Builder instead of a mutable ArrayList to build the list of release links for better performance and consistency with the codebase.

[jinseopkim0]

/gemini review

[gemini-code-assist]

Code Review

This pull request simplifies the release note generation process by removing support for split repositories (such as bigtable, firestore, pubsub, and pubsublite) and focusing solely on the monorepo. It removes unused imports, the splitRepositoryLibraryNames set, the releaseUrlForSplitRepo method, and refactors reportClientLibrariesNotableChangeLogs and releaseUrlForMonorepo to eliminate split repository logic. I have no feedback to provide.