Backport 19.0 of "Fix infinite retry on detected language rename"

What does this MR do and why?

Original issue: Permanently failing sidekiq task due to renamin... (#602294 - closed)

When Gitaly returns a new canonical name for a language whose language_id already exists under a different ProgrammingLanguage name, repository language detection repeatedly failed on the unique language_id constraint and retried forever, stalling Sidekiq.

Includes the two supporting refactors (detected language objects and the extracted ProgrammingLanguageResolver) required for the fix to apply cleanly.

It's a combination of MRs:

• !241475 (merged)
• !241485 (merged)
• !241512 (merged)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
• The MR title is descriptive (e.g. "Backport of 'title of default branch MR'"). This is important, since the title will be copied to the patch blog post.
• Required labels have been applied to this merge request
  • severity label and bug subtype labels (if applicable)
  • If this MR fixes a bug that affects customers, the customer label has been applied.
• This MR has been approved by a maintainer (only one approval is required).
• Ensure the e2e:test-on-omnibus-ee job has succeeded, or if it has failed, investigate the failures. If you determine the failures are unrelated, you may proceed. If you need assistance investigating, request help in the #s_developer_experience Slack channel to confirm the failures are unrelated to the merge request.

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
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• Once the backport has been merged, the commit changes will be automatically deployed to a release environment that can be used for manual validation. See after merging runbook for details.