As we always call both methods from the controller - and elsewhere we call the
more general method - and one uses all notes and the other uses system notes,
then we should just load the notes and their authors once, and filter on the
Ruby side.

Whether the preloading belongs in the service or the controller is arguable,
here. As the service is only used for one controller action, it seems reasonable
to put it in the service, but that is not a definitive answer.

Adding the preloads for MR project routes here doesn't seem to work, perhaps
because of https://github.com/rails/rails/issues/32140.

Sorting here needs the project routes to be loaded, including the namespace
routes.

`#referenced_merge_requests` preloaded too many associations. Award emoji, for
instance, are completely unnecessary here.

`#closed_by_merge_requests` had the opposite problem: `#all_references` needs
each item's author, and these weren't preloaded.

These methods don't really need to be on the Issue model. Issue#related_branches
can also be moved to a service, but we can do that in a separate commit.

This commit does not change any behaviour; it just moves code around, renames
the service, and refactors the specs.

Fixed deleting new files creating wrong state in IDE

Closes #50255

See merge request gitlab-org/gitlab-ce!21225

Added missing html_safe on text messages.

See merge request gitlab-org/gitlab-ce!21232

Enable frozen in app/mailers/**/*.rb

See merge request gitlab-org/gitlab-ce!21147

Add Acceptance testing issue template

See merge request gitlab-org/gitlab-ce!21156

Core backports from the Premium license templates feature

See merge request gitlab-org/gitlab-ce!21212

Duplicate specs testing emoji awards on issues

Closes #45238

See merge request gitlab-org/gitlab-ce!21126

Closes #50255

Add author-link style from common.scss in EE

See merge request gitlab-org/gitlab-ce!21204

Reduce number of model instances needed in test.

Closes #49788

See merge request gitlab-org/gitlab-ce!21192

Add Czech as an available language

Closes #43227

See merge request gitlab-org/gitlab-ce!21201

Documentation for JUnit XML Test Summary In MR widget

Closes #49867

See merge request gitlab-org/gitlab-ce!21061

Port EE changes for mirrors/_instructions.html.haml

See merge request gitlab-org/gitlab-ce!21107

Add a "user_show_add_ssh_key_message" application setting for use with SSH certificates

Closes #49953

See merge request gitlab-org/gitlab-ce!21027

New translations added to `locale/cs_CZ` will automatically be picked up.

Closes #49788.

Backport of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6860

See merge request gitlab-org/gitlab-ce!21200

Creates vue component for artifacts block

See merge request gitlab-org/gitlab-ce!21198

chore(docs): add field repository_update_events

See merge request gitlab-org/gitlab-ce!21205

Fix `bin/secpick` rainbow gem error, and security branch prefixing

See merge request gitlab-org/gitlab-ce!21210

Resolve "JS Pages do not load on windows 8, IE 11"

Closes #50281

See merge request gitlab-org/gitlab-ce!21214

Vendor in Auto-DevOps.gitlab-ci.yml to update glibc to 2.28

Closes #50294

See merge request gitlab-org/gitlab-ce!21191

MR Page incremental rendering

See merge request gitlab-org/gitlab-ce!21063

Modified find project method to return nil if project not found

See merge request gitlab-org/gitlab-ce!21168