This reverts commit ec4730478b798270781257913ee4cede673d4d4e.

This implements Repository#ambiguous_ref? and checks if a ref is
ambiguous before trying to resolve the ref in Project#protected_for?

Reworks Project#resolve_ref to return Gitlab::Git::Branch,
Gitlab::Git::Tag or raise an AmbiguousRef error.

CE Backport: Epic issue list and related issue list re-design

See merge request gitlab-org/gitlab-ce!23658

Resolve "Navigating unresolved discussions on Merge Request page"

Closes #51122

See merge request gitlab-org/gitlab-ce!22789

Resolve "Extended user centric tooltips"

Closes #50157

See merge request gitlab-org/gitlab-ce!23231

[CE] Backport SAML unlink changes: UrlBlocker#ascii_only

See merge request gitlab-org/gitlab-ce!23627

Resolve "Utilize new charting library for metrics dashboard"

See merge request gitlab-org/gitlab-ce!23459

Integrate csslab

Closes csslab#1

See merge request gitlab-org/gitlab-ce!23521

Fix for incorrect Correlation-ID key being passed through GRPC metadata

Closes #55054

See merge request gitlab-org/gitlab-ce!23666

Add Kushal to frontend CODEOWNERS

See merge request gitlab-org/gitlab-ce!23664

Fill project_repositories for hashed storage projects

Closes #48527

See merge request gitlab-org/gitlab-ce!23482