Adds a feature flag to the optimization done for store_mentions!

This is needed for the UPSERT to work properly since we're detecting a
unique constraint conflict on [noteable_id, note_id]

Changelog: other

Using UPSERT saves us a query, avoids cases where we get
RecordNotUnique, and removes the use of SAVEPOINT which can cause PG
performance issues.

Speed up backend tests in Gitpod environment

See merge request gitlab-org/gitlab!68482

Fix and reschedule background migration for backfilling data from `ci_builds` to `security_scans`

See merge request gitlab-org/gitlab!68305

Fix mobile layout issues in notes form

See merge request gitlab-org/gitlab!68414

Add coverage regex for Rust's tarpaulin

See merge request gitlab-org/gitlab!68469

Added reason for using backticks for text entered in UI

See merge request gitlab-org/gitlab!68486

Consolidate project and group can admin members helpers

See merge request gitlab-org/gitlab!64950

Add missing suffixes to notification mails

See merge request gitlab-org/gitlab!64767

- Fix alignment issue in toggle thread button
- Fix broken markdown toolbar layout in snippets
comments

Changelog: fixed

Update create merge request button on last push event

See merge request gitlab-org/gitlab!63103

Changelog: changed

Fix intermittent 'branch not found' errors when pushing creates an MR

See merge request gitlab-org/gitlab!68362

Remove subtransaction from HistoricalStatistics

See merge request gitlab-org/gitlab!68124

Add missing Ci::Build graphql mutations

See merge request gitlab-org/gitlab!68399

Changelog: added

Remove redundant Debian API instructions

See merge request gitlab-org/gitlab!68495

Document the use of create_or_find_by in SQL-docs

See merge request gitlab-org/gitlab!68245

Linear version of Project#ancestors

See merge request gitlab-org/gitlab!68072

Changelog: performance

Reduce subtransactions in safe_find_or_create_by

See merge request gitlab-org/gitlab!68458

Add dependency proxy docs to deploy tokens

See merge request gitlab-org/gitlab!68198

Add note about allowed overage

See merge request gitlab-org/gitlab!68402

Update Gitaly version

See merge request gitlab-org/gitlab!68483

Pass keyword args explicitly

See merge request gitlab-org/gitlab!68425

Add Cloud Native Hybrid instructions on 2k users RA page

See merge request gitlab-org/gitlab!67778

Fixes vale warnings for Slony documentation

See merge request gitlab-org/gitlab!68221

Fix source installation docs and init script for gitlab-pages

See merge request gitlab-org/gitlab!67744

Clarify pull mirroring interval usage

See merge request gitlab-org/gitlab!68443

Add caching guidelines

See merge request gitlab-org/gitlab!63971