Add documentation on epic add/remove child relations quick actions

See merge request gitlab-org/gitlab-ce!29860

Use next_instance_of instead of any_instance_of

See merge request gitlab-org/gitlab-ce!29905

Backport changes made by EE to various YAML configuration files

See merge request gitlab-org/gitlab-ce!29606

For prepended classes, we need to use `expect_next_instance_of`
instead of RSpecs `any_instance_of` variants.

Errors in application settings panel shows wrong panel

See merge request gitlab-org/gitlab-ce!25434

Fixed failing GraphQL file import

Closes #63527

See merge request gitlab-org/gitlab-ce!29900

Improve bug severity definitions and consolidate guidance for clarity

See merge request gitlab-org/gitlab-ce!29694

Add embedding support to metrics_dashboard

See merge request gitlab-org/gitlab-ce!29696

This commits adds support for metrics dashboards
for embedding. If the flag 'embedded' is provided
to the environments/id/metrics_dashboard endpoint,
the response will be suitable for embedding in
issues or other content.

This is a precursor for support for embedding
metrics in GFM.