Add API routes to lock and unlock issues (#34165)

This pull request adds a GitHub-compatible API endpoint to lock and
unlock an issue.

The following routes exist now:
- `PUT /api/v1/repos/{owner}/{repo}/issues/{id}/lock` to lock an issue
- `DELETE /api/v1/repos/{owner}/{repo}/issues/{id}/lock` to unlock an issue

Fixes #33677
Fixes #20012

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

options/locale/locale_en-US.ini

@@ -1681,7 +1681,6 @@ issues.pin_comment = "pinned this %s"
 issues.unpin_comment = "unpinned this %s"
 issues.lock = Lock conversation
 issues.unlock = Unlock conversation
-issues.lock.unknown_reason = Cannot lock an issue with an unknown reason.
 issues.lock_duplicate = An issue cannot be locked twice.
 issues.unlock_error = Cannot unlock an issue that is not locked.
 issues.lock_with_reason = "locked as <strong>%s</strong> and limited conversation to collaborators %s"