Standardize branch name params as `branch` on V4 API
This MR enforces the pattern of using
branch_name on our V4 API params.
- Changelog entry added
- Documentation created/updated
- API support added
- Added for this feature/bug
- All builds are passing
- Conform by the merge request performance guides
- Conform by the style guides
Branch has no merge conflicts with
master(if it does - rebase it please)
- Squashed related commits together
What are the relevant issue numbers?
Closes #22132 (closed)