[CE] Add mutually exclusive labels

See merge request gitlab-org/gitlab-ce!26804

Replaces blockquote fences with \n,
keeping the line numbering intact.

- added suggestions to mock data
- fixed props to be not required

Scoped labels in EE require additional changes in CE code.

Adds the groundwork needed in order to persist multi-line suggestions,
while providing the parsing strategy which will be reused for the
**Preview** as well.

Resolve "Extended tooltip for merge request links"

Closes #54916

See merge request gitlab-org/gitlab-ce!25221

- Show pipeline status, title, MR Status and project path
- Popover attached to gitlab flavored markdown everywhere, including:
  + MR/Issue Title
  + MR/Issue description
  + MR/Issue comments
  + Rendered markdown files

Implements the filtering logic for
`suggestion:-x+y` syntax.

Prior to this change, 35 Gitaly RPCs were allowed. But recently there's
been a renewed interest in performance. By lowering the number of
calls new N + 1's will pop up.

Later commits will add blocks to ignore the raised errors, followed by
an issue for each to be fixed.