Merge branch '466147-render-head-diff-diffs-stream' into 'master'

Support rendering HEAD diff in diffs streaming endpoint

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/160365



Merged-by: Stan Hu <stanhu@gmail.com>
Approved-by: Sincheol (David) Kim <dkim@gitlab.com>
Approved-by: Stan Hu <stanhu@gmail.com>
Co-authored-by: Patrick Bajao <ebajao@gitlab.com>