This commit handles note diffs caching, which considerably improves
the performance on merge requests with lots of comments.
Important to note that the caching approach taken here is different
from `Gitlab::Diff::HighlightCache`. We do not reset the whole cache
when a new push is sent or anything else. That's because discussions
diffs are persisted and do not change.

Updates gitlab ui to v1.18.0

See merge request gitlab-org/gitlab-ce!23983

[ci skip]

Rename `ClusterPlatformConfigureWorker`

Closes #54863

See merge request gitlab-org/gitlab-ce!23754

Fixes the markdown toolbar buttons

Closes #55618

See merge request gitlab-org/gitlab-ce!23979

Option to make variables protected by default

Closes #51822

See merge request gitlab-org/gitlab-ce!22744

Resolve "Wrong API call on releases page"

Closes #55639

See merge request gitlab-org/gitlab-ce!23978

Resolve "Split bio into individual line in extended user tooltips"

Closes #55293

See merge request gitlab-org/gitlab-ce!23940

Add date range to milestone changed emails

Closes #53933

See merge request gitlab-org/gitlab-ce!23762

Clarify where the k8s applications can be found

Closes #42262

See merge request gitlab-org/gitlab-ce!23914

(CE-Port) Support navbar tracking

See merge request gitlab-org/gitlab-ce!23975

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55618

- Remove leading 'at' in organzation info
- Update karma tests

Also refactored issues and MRs to use the same email template file

Rails5: convert specs in javascripts/ and support/ to new spec syntax

See merge request gitlab-org/gitlab-ce!23947

- Add tracking attributes to templates

Update minimum version of nokogiri in Gemfile also

See merge request gitlab-org/gitlab-ce!23829

[master] Persistent Symlink in Project Import

See merge request gitlab/gitlabhq!2673

Fix notification email for image diff notes

See merge request gitlab-org/gitlab-ce!23958

Always load the metrics the last

Closes #55611

See merge request gitlab-org/gitlab-ce!23960

Display commit ID for discussions made on merge request commits

Closes #53953

See merge request gitlab-org/gitlab-ce!23837

Fixes: ActionView::Template::Error (undefined method `add_class' for #<Nokogiri::XML::Element:0x0055dbff5252e8>

Fix typos about .gitlab-ci.yml in Serverless docs

See merge request gitlab-org/gitlab-ce!23963

Fixes a bug where merge request comments made
in the context of a specific commit no longer specify
which commit they were created on

Display "commented" only for commit discussions on merge requests

Closes #53950 and #53681

See merge request gitlab-org/gitlab-ce!23622

Use px instead of rems to prep for csslab

Closes #55314

See merge request gitlab-org/gitlab-ce!23804

Fix line-height of line numbers

Closes #55278 and #51668

See merge request gitlab-org/gitlab-ce!23775

Fix broken link in feature proposal template

See merge request gitlab-org/gitlab-ce!23957

[ci skip]

Resolve "build-loader-animation dots misaligned"

Closes #52620

See merge request gitlab-org/gitlab-ce!23959

Remove deprecated xhr from specs

Closes #55448

See merge request gitlab-org/gitlab-ce!23949

[ci skip]