Closes #42800.

Rather radical but avoids n+1 queries in the rather common case we want
to include information about the author.

We want to drop the generic #avatar_icon helper that supports both an email
and a user object being passed in. Instead, we want to explicitly use the #avatar_icon_for_user
and #avatar_icon_for_email helpers depending on what we have at hand.
This allows us to avoid unnecessary database queries (e.g. call
User.find_by_any_email if we already have the user).

In situations like here, this makes it less convenient to use.

We need to keep the email lookup as we want to fall back to displaying
the gravatar result for a given email if the user does not exist.

Whenever we already deal with a User object, let's use the more specific
method avatar_icon_for_user.

When we don't use the original `ApplicationHelper#avatar_icon` anymore, we
can just remove it (and its specs).

Closes #42800.

Group MR numbers on issue show page by project and namespace

Closes #26466

See merge request gitlab-org/gitlab-ce!8494

Closes #26466.

Fix artifact creation in CI/CD QA spec

See merge request gitlab-org/gitlab-ce!17078

Port of EE-translations

See merge request gitlab-org/gitlab-ce!17081

Resolve "PrepareUntrackedUploads PostgreSQL syntax error"

Closes #42881

See merge request gitlab-org/gitlab-ce!17019

Resolve "Can't close issue through buttons in the textarea on mobile"

Closes #42923

See merge request gitlab-org/gitlab-ce!17043

Disable caching of tables for migration spec that drops a temporary table

See merge request gitlab-org/gitlab-ce!16965

Fix Error 500s creating merge requests with external issue tracker

Closes #43193

See merge request gitlab-org/gitlab-ce!17073

Cleanup new branch/merge request form in issues

Closes #41938

See merge request gitlab-org/gitlab-ce!16854

* master: (25 commits)
  Addressed mr observations
  Clean new Flash() and stop disabling no-new (eslint) when possible
  Disable query limiting warnings for now on GitLab.com
  Revert "Merge branch 'rd-40552-gitlab-should-check-if-keys-are-valid-before-saving' into 'master'"
  Fix warning messages for promoting labels and milestones
  Fixed missing js selector for the realtime pipelines commit comp
  Honour workhorse provided file name
  Create an empty wiki when there is no wiki in the gitlab export bundle
  Revert and remove header_title line from labels issue
  Fixed bug with param config
  changed params passed to from a string to an object
  Move IssuableTimeTracker vue component
  Fix breadcrumb on labels page for groups
  Convert groups_select ajax to use axios
  Default CI variables to unprotected
  make sure there is a dependency on Gitlab::CurrentSettings is
  Make GITLAB_FEATURES in build_spec compatible with EE
  Update jquery.waitforimages & use npm version
  Fixed typo, updated test, and removed commented code
  Replaced use of $.get with axios.get and updated tests
  ...

New Crowdin translations

See merge request gitlab-org/gitlab-ee!4481

When JIRA or Redmine were enabled and the branch name did not match the
matching regular expression, the `issue_iid` would be `nil`, preventing
users from creating merge requests.

Closes #43193

Updated katex library

Closes #43032

See merge request gitlab-org/gitlab-ce!15864

Clean new Flash() and stop disabling no-new (eslint) when possible

Closes #42732

See merge request gitlab-org/gitlab-ce!17060

Disable query limiting warnings for now on GitLab.com

See merge request gitlab-org/gitlab-ce!17067

Honour workhorse provided file name

See merge request gitlab-org/gitlab-ce!17059

Fix warning messages for promoting labels and milestones

Closes #42900

See merge request gitlab-org/gitlab-ce!17063

Merge branch 'rd-43185-revert-sanitize-extra-blank-spaces-used-when-uploading-a-ssh-key' into 'master'

Revert "Merge branch 'rd-40552-gitlab-should-check-if-keys-are-valid-before-saving' into 'master'"

See merge request gitlab-org/gitlab-ce!17062

To finish migrating untracked files to uploads for installations that were affected by https://gitlab.com/gitlab-org/gitlab-ce/issues/42881

Or just to delete the temp table if it is empty and left behind.