feat: Add block on pending codeowner reviews branch protection (#34995)

This commit introduces a new branch protection rule that allows merge
blocking if there are pending reviews from one or more code owners (as
defined in any valid `CODEOWNERS` file). This is determined by
evaluating each rule present in the `CODEOWNERS` file individually. For
every rule, at least one named code owner (or member of a code owner
team) must have given an approving review for merging to be possible.

Closes #32602 

---

This PR does NOT display code owners separately from other reviewers
(#28137)

### Screenshot

<details>
<summary>Pull Request</summary>
<img
src="https://github.com/user-attachments/assets/74560f9c-9f59-477a-b270-63f937b26d6a"
/>
</details>

<details>
<summary>Branch Protection Rule</summary>
<img
src="https://github.com/user-attachments/assets/f0a9ce00-38fe-4eed-b6a3-5290aa404610"
/>
</details>

Doc PR
https://gitea.com/gitea/docs/pulls/245

---------

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

services/pull/merge.go

@@ -602,6 +602,10 @@ func CheckPullBranchProtections(ctx context.Context, pr *issues_model.PullReques
 		return util.ErrorWrap(ErrNotReadyToMerge, "The head branch is behind the base branch")
 	}
 
+	if !issue_service.HasAllRequiredCodeownerReviews(ctx, pb, pr) {
+		return util.ErrorWrap(ErrNotReadyToMerge, "There are missing code owner reviews")
+	}
+
 	if skipProtectedFilesCheck {
 		return nil
 	}