This commits prepares the database load balancing code for always being
enabled, even when no replicas are configured.

To achieve this, the load balancer now supports the "primary_only"
option. When enabled, the list of replicas is ignored (which is empty
anyway), and a fake replica is used instead. This fake replica simply
reuses the primary connection of the load balancer it belongs to. We
chose this approach as there's simply too much code that assumes at
least one replica is present when load balancing is enabled.

In addition, we make various changes to ConnectionProxy to allow us to
always enable the use of this class. As an example, some tests use code
like this:

    ActiveRecord::Schema.define do
      create_table :foo do
        ...
      end
    end

Internally Rails ends up performing some `respond_to?` checks to expose
certain methods (or not). Without defining a custom
`respond_to_missing?`, these checks return `false` and thus the method
isn't available.

We've also had to change a few more methods in the ConnectionProxy
object to handle forwarding trailing hashes. In the previous setup
certain tests would still trigger deprecation warnings. This can be
avoided by using `...` everywhere, and getting rid of the `sticky:`
keyword argument.

Changelog: changed

Update dependency prosemirror-markdown to ^1.5.2

See merge request gitlab-org/gitlab!69547

Refactor labels dropdown to GlDropdown

See merge request gitlab-org/gitlab!69263

Repurpose Gitaly SRE Subpage to GitLab AWS SRE Subpage

See merge request gitlab-org/gitlab!69250

Update dependency @gitlab/ui to v32.5.0

See merge request gitlab-org/gitlab!69381

Make sure we respect bundler config for Gemfile

See merge request gitlab-org/gitlab!69461

Spell out first use of DVCS in Jira docs

See merge request gitlab-org/gitlab!69534

Externalize page-title messages

See merge request gitlab-org/gitlab!69124

RuboCop: Ban more methods which might cause subtransactions

See merge request gitlab-org/gitlab!69315

Docs: improve code_review page

See merge request gitlab-org/gitlab!69334

Clarify use of resolvers in code

See merge request gitlab-org/gitlab!69458

Allow callsite in project for cross-database queries

See merge request gitlab-org/gitlab!69447

Add relationship between project and project namespace

See merge request gitlab-org/gitlab!68825

Fix a flaky time expectation and a flaky ordering-related expectation

See merge request gitlab-org/gitlab!69450

Add milestone to license metrics

See merge request gitlab-org/gitlab!69398

Remove integrated_error_tracking feature flag

See merge request gitlab-org/gitlab!69303

Mark feature flags in Gitlab/MarkUsedFeatureFlags only once

See merge request gitlab-org/gitlab!69469

Support multiple wal locations for each database

See merge request gitlab-org/gitlab!69371

Update help text for API Fuzzing Configuration

See merge request gitlab-org/gitlab!69429

Make the credit card validation alert dismissible

See merge request gitlab-org/gitlab!69245

Integrated error tracking feature is available to users. It still needs
to be enabled per project. See documentation.

Changelog: removed
Signed-off-by: Dmytro Zaporozhets <dzaporozhets@gitlab.com>

- Add ProjectNamespace model in Namespaces
- Add foreign key

Changelog: added

Use linear version GroupsWithTemplatesFinder#extended_group_search

See merge request gitlab-org/gitlab!68936

Revert "Validate user website_url"

See merge request gitlab-org/gitlab!69532

Mark the `PostReceive` worker as idempotent

See merge request gitlab-org/gitlab!69305

Fix flaky order-dependent assertions

See merge request gitlab-org/gitlab!68516

Refresh CI minutes cache after updating limits

See merge request gitlab-org/gitlab!69443

Clear memoization of a stubbed object

See merge request gitlab-org/gitlab!69521

Add milestone <13.9 to metrics with no milestone

See merge request gitlab-org/gitlab!69400

Fix contextual help link and other minor improvements

See merge request gitlab-org/gitlab!68838

Telemetry of false-positive flag for vulnerability_finding

See merge request gitlab-org/gitlab!68184

Delete legacy board store and models [RUN AS-IF-FOSS]

See merge request gitlab-org/gitlab!69423

Cross link between related topics

See merge request gitlab-org/gitlab!68817

Update pages docs with info about geo setup

See merge request gitlab-org/gitlab!67901