- Avoid N+1 queries for authors and comment counts
- Avoid an additional snippet existence query

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

Before, the styling for `img:not(.emoji)`` was repeated between
`.md:not(.use-csslab):not(.wiki)` (for comments and the Markdown
preview), `.documentation.wiki` (for help pages), and
`.issuable-details .description .wiki` (for MR and issue descriptions).

In these places, we now simply use `.md`. Wherever we use `.md` but
don't want this image styling (like wikis and blobs), `.md-file` is
added.

Add "smoke" tag to the test

Fix links to views in Page Object files

Review fixes

Remove useless view block

Implement Snippets::Show page object class

Fix review suggestions

Fix review suggestions 2

Fix test with empty snippets state

Remove useless css class

Fix issues

This engine was replaced with CommonMarker in 11.4, it was deprecated
since then.

Rename btn-new, btn-create and btn-save to btn-success

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

The status is shown for
- The author of a commit when viewing a commit
- Notes on a commit (regular/diff)
- The user that triggered a pipeline when viewing a pipeline
- The author of a merge request when viewing a merge request
- The author of notes on a merge request (regular/diff)
- The author of an issue when viewing an issue
- The author of notes on an issue
- The author of a snippet when viewing a snippet
- The author of notes on a snippet
- A user's profile page
- The list of members of a group/user