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Allow custom hooks errors to appear in GitLab UI

Closes #48132

See merge request gitlab-org/gitlab-ce!25625

Remove .raw from JavaScript fixture file names

Closes #59201

See merge request gitlab-org/gitlab-ce!26430

(cherry picked from commit 79a45f7f02939a1c2fc1f378e43ec9b96630f918)

Error messages from custom pre-receive hooks now appear in the GitLab
UI.

This is re-enabling a feature that had been disabled in merge request
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18646

The feature had been disabled due to security concerns that information
which was not intended to be public (like stack traces) would leak into
public view.

PreReceiveErrors (from pre-receive, post-receive and update custom
hooks) are now filtered for messages that have been prefixed in a
particular way.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/48132

This reverts merge request !26430

Remove .raw from JavaScript fixture file names

Closes #59201

See merge request gitlab-org/gitlab-ce!26430

There is nothing more to say but

"Commits that change 30 or more lines across at least three files
must describe these changes in the commit body"

This commit updates the pipeline block that appears on the merge request
page to include information that will be exposed by the API as part of
the post-merge pipeline feature.

Update dependency @gitlab/ui to ^2.3.0

See merge request gitlab-org/gitlab-ce!26181