Fix CODEOWNERS review request attribution using comment metadata (#36348)

Fixes #36333

## Problem

When CODEOWNERS automatically assigns reviewers to a pull request, the
timeline incorrectly shows the PR author as the one who requested the
review (e.g., "PR_AUTHOR requested review from CODE_OWNER"). This is
misleading since the action was triggered automatically by CODEOWNERS
rules, not by the PR author.

## Solution

Store CODEOWNERS attribution in comment metadata instead of changing the
doer user:
- Add `SpecialDoerName` field to `CommentMetaData` struct (value:
`"CODEOWNERS"` for CODEOWNERS-triggered requests)
- Pass `isCodeOwners=true` to `AddReviewRequest` and
`AddTeamReviewRequest` functions
- Template can check this metadata to show appropriate attribution
message

---------

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

options/locale/locale_en-US.json

@@ -1702,6 +1702,7 @@
   "repo.issues.review.content.empty": "You need to leave a comment indicating the requested change(s).",
   "repo.issues.review.reject": "requested changes %s",
   "repo.issues.review.wait": "was requested for review %s",
+  "repo.issues.review.codeowners_rules": "CODEOWNERS rules",
   "repo.issues.review.add_review_request": "requested review from %s %s",
   "repo.issues.review.remove_review_request": "removed review request for %s %s",
   "repo.issues.review.remove_review_request_self": "declined to review %s",