This should reduce the number of SQL queries and lookups needed to look up a
project of a build and pipeline and vice versa.

Before:

```
[1] pry(main)> Ci::Build.reflect_on_association(:project).has_inverse?
=> false
[2] pry(main)> Project.reflect_on_association(:builds).has_inverse?
=> false
[3] pry(main)> Ci::Pipeline.reflect_on_association(:project).has_inverse?
=> false
[4] pry(main)> Project.reflect_on_association(:pipelines).has_inverse?
=> :project
```

After:

```
[1] pry(main)> Ci::Build.reflect_on_association(:project).has_inverse?
=> :builds
[2] pry(main)> Project.reflect_on_association(:builds).has_inverse?
=> :project
[3] pry(main)> Ci::Pipeline.reflect_on_association(:project).has_inverse?
=> :pipelines
[4] pry(main)> Project.reflect_on_association(:pipelines).has_inverse?
=> :project
```

Resolve "Use toggle for subscribed/unsubscribed to notifications"

Closes #16988

See merge request gitlab-org/gitlab-ce!16408

Rename ~Prometheus to ~Monitoring

See merge request gitlab-org/gitlab-ce!16442

fix gitlab-org/gitlab-ce#41891 (design nitpick)

Closes #41891

See merge request gitlab-org/gitlab-ce!16383

Display related merge requests in commit detail page

Closes #2383

See merge request gitlab-org/gitlab-ce!13713

Refactor projects:l*

See merge request gitlab-org/gitlab-ce!16393

Move row containing Projects, Users and Groups count to the top

Closes #40492

See merge request gitlab-org/gitlab-ce!16421

Generalize protected branch/tag dropdowns -- CE backport

See merge request gitlab-org/gitlab-ce!16420

Introduce PredicateMemoization cop

Closes #41731

See merge request gitlab-org/gitlab-ce!16329

* upstream/master:
  Docs: move article "Autoscaling Runners on AWS" to its topic-related dir
  Update missing API documentation on `GET /users/:id/projects`
  Docs: remove duplicate CI examples
  Only search for MR revert commits on notes after MR was merged
  Added .rej files to gitignore
  Fixed performance of projects dropdown
  Add a note about GitLab QA page objects validator to docs
  Refactor dispatcher projects blame and blob path
  Fix Ctrl+Enter keyboard shortcut saving comment/note edit
  Fix boolean prop being provided as string
  Fixes minor aspects on Prometheus description
  Refactor dispatcher project branches path
  Use simple Next/Prev paging for jobs to avoid large count queries on arbitrarily large sets of historical jobs
  Update the grpc gem to 1.8.3

Resolve "!15665 consistently 502s because it fetches every commit"

Closes #41807

See merge request gitlab-org/gitlab-ce!16320

Docs: move article "Autoscaling Runners on AWS" to its topic-related dir

See merge request gitlab-org/gitlab-ce!16368

Fixed performance of projects dropdown

Closes #41939

See merge request gitlab-org/gitlab-ce!16425

Use simple Next/Prev paging for CI Jobs page

Closes #41058

See merge request gitlab-org/gitlab-ce!16392

Update missing API documentation on `GET /users/:id/projects`

Closes #41478

See merge request gitlab-org/gitlab-ce!16363

Docs: remove duplicate CI examples

Closes #41872

See merge request gitlab-org/gitlab-ce!16372

If we search for notes before the MR was merged, we have to load every commit
that was ever part of the MR, or mentioned in a push. In extreme cases, this can
be tens of thousands of commits to load, but we know they can't revert the merge
commit, because they are from before the MR was merged.

In the (rare) case that we don't have a `merged_at` value for the MR, we can
still search all notes.

Added .rej files to gitignore

See merge request gitlab-org/gitlab-ce!16429

Resolve "Fix type is started key"

Closes #41937

See merge request gitlab-org/gitlab-ce!16407

[ci skip]

Resolve "Wording fixes on cluster page"

Closes #41797

See merge request gitlab-org/gitlab-ce!16324

Closes #41939

Update the grpc gem to 1.8.3

See merge request gitlab-org/gitlab-ce!16354