Resolve "Cross-project pipelines are broken"

Closes #2682

See merge request !2166

Fix avatar images in pipeline and approval emails

See merge request !2182

Fix some failing specs on master

Closes #2694

See merge request !2180

Add docs for multi-project pipelines graphs

See merge request !2136

Add link to issue for MySQL/subgroups drop support

See merge request !2184

Fix quoted example in triggers docs

Closes #2686

See merge request !2171

Mention limitations of MySQL in docs

See merge request !2165

Add info about artifacts object storage in docs

Closes #2311

See merge request !2147

Change a few missing `login_as` to `gitlab_sign_in`

See merge request !2176

[EE] Prepare for bypassing GitLab sign in in feature specs

See merge request !2140

Enable autocomplete on project snippets -- EE merge edition

See merge request !2174

CE upstream: Thursday

Closes gitlab-ce#31782, gitlab-ce#33529, gitlab-ce#32861, gitlab-ce#33483, #2525, gitlab-ce#31263, gitlab-ce#33403, and gitlab-ce#33106

See merge request !2137

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1210 disabled
autocomplete for personal snippets and project snippets. But we want
autocomplete on project snippets.

Disable autocomplete on snippets comments -- EE merge edition

Closes gitlab-ce#33594

See merge request !2167

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/2686

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/33594

Was supposedly fixed in MR for
https://gitlab.com/gitlab-org/gitlab-ce/issues/32086 but seeing this pop
up again

adds prometheus metrics to both mirro and remote mirror features

See merge request !2118

removes ignore column sync time logic from remote mirror model

See merge request !1850

Not sure why this fails with the full login flow, but it's not necessary
and would've been changed eventually anyway, so whatever!

Change `logout_direct` uses to `gitlab_sign_out_direct`

Change single `login_via` use to `gitlab_sign_in_via`

- [x] Rename `login_as` to `gitlab_sign_in`
- [x] Rename `login_with` to `gitlab_sign_in_with`
- [x] Rename `login_via` to `gitlab_sign_in_via`
- [x] Rename `logout` to `gitlab_sign_out`
- [x] Rename `logout_direct` to `gitlab_sign_out_direct`
- [x] Make `gitlab_login_with` (née `login_with`) private
- [x] Make `mock_auth_hash` private

Document the Delete Merged Branches functionality

See merge request !2149