[chore](ci) Require TeamCity/external on master, branch-4.2 and branch-4.1 - #70578

…h-4.1

### Background

The required status checks of every protected branch come from `protected_branches` in the `.asf.yaml` on `master`. ASF's asfyaml service applies that section to GitHub whenever the `github:` block changes; the copies on release branches have no effect. Since apache#70459, PRs into `master`, `branch-4.2` and `branch-4.1` are checked by the new TeamCity, which reports statuses named `TeamCity/<pipeline>`. External is the regression lane for external catalogs and their docker fixtures.

### What problem does this PR solve?

Issue Number: None
Related PR: apache#70459 (introduced the behavior this PR changes), apache#70457 (must be picked to branch-4.2 and branch-4.1 first)
PR Type: Build/CI/Chore

Problem Summary:

When apache#70459 renamed the required checks, it left `TeamCity/external` out, so a red External run no longer blocks merges into `master`, `branch-4.2` or `branch-4.1`. This PR adds it back to all three lists, in the slot the old `External Regression (Doris External Regression)` check had. Merging also makes asfyaml re-apply the whole section, and GitHub is out of sync with it today: `branch-4.2` still requires the nine pre-migration names, which new PRs never receive, and `branch-4.1` and `branch-2.0` have no protection at all.

### Details

- **Affected:** GitHub branch protection only: one more required context on `master` (17 in total), `branch-4.2` (13) and `branch-4.1` (13). No workflow, script or TeamCity change: External uses P0's file filter, so a PR that skips P0 also gets a skipped `TeamCity/external`. Trailing spaces are dropped from two `branch-4.0` and `branch-3.1` lines, which changes no value.
- **Developer and release impact:** PRs into the three branches need `TeamCity/external` green or skipped before they can merge. On `branch-4.2` and `branch-4.1` its preflight fails today with `Native rootless support missing; cherry-pick PR70457 before validating this branch`, so apache#70457 has to be picked to both branches before this lands, or every 4.x PR that runs External is blocked. Once protection is re-applied, `branch-4.1` PRs again need an approval and green required checks, and `branch-4.2` PRs can merge on the `TeamCity/*` checks they actually receive.
- **License and third-party:** None.
- **Rollback:** Revert this commit; asfyaml applies the previous lists again because the `github:` block changes.

### Testing

- `asfyaml-validate` from apache/infrastructure-asfyaml (`e4c2644`), run locally: the old and the new file are valid, and copies with a non-integer review count or a mis-indented list item are rejected.
- Both files parsed locally with asfyaml's GitHub schema: the only data change is `TeamCity/external` in the three `contexts` lists, with the existing order kept and no duplicates.
- Every name in the new lists is reported on live PRs: all 17 on apache#70366 (`master`), and all 13 on a recent `branch-4.1` PR.

### Notes for Reviewers

- asfyaml runs only on `master`, after the merge, so whether GitHub takes the new lists can only be checked then: `gh api repos/apache/doris/branches/<branch> --jq .protection.required_status_checks.contexts` for each branch, and `.protected` for `branch-4.1` and `branch-2.0`. A failed run is mailed to [email protected] and to whoever merged.
- `TeamCity/performance` stays optional; the comment above the lists now says only that.

### Release note

None

### Check List (For Author)

- Behavior changed: No
- Does this need documentation: No
- Pre-submission status: Partially verified: the file passes ASF's validator, but whether asfyaml applies it to GitHub can only be checked after the merge.

### AI Disclosure

- Tool: Claude Code (Claude Opus 5.5)
- Generated: the `.asf.yaml` change and this description
- Human review: not stated
- Prompts: Asked why `TeamCity/external` is not a required check on apache#70366, then to make it required again and fix the out-of-sync protection of `branch-4.1` and `branch-4.2`, changing only `.asf.yaml` and listing any 4.x cherry-picks for the author to handle.

Co-Authored-By: Claude Opus 5.5 <[email protected]>