This updates the groups list UI to match the style of the project list:

- New layout
- Improve loading state when loading group children
- Larger, responsive text
- Icon and text colors changed to secondary
- Smaller button sizes
- Content list description colors were standardized to body text

Turn avatar-counter into a mixin with optional border-radius

CE Port

**Why?**
The styles applied to `.build-page .top-bar` were mostly
unecessary for the IDE terminal. The static positioning might
have also been causing a strange line to show up in the terminal.

Moved all avatar related styles to the components directory

Use gray-600 for color
Ensure passes accessibility reqs

When https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4765 was
created, comments were wrapped in `.note-text`, while Markdown previews
were wrapped in `.md.md-preview-holder`. Both `.note-text` and `.md`
included the `md-typography` mixin, but for some reason the bulleted
list styling had previously been only under `.note-text`, rather than
`md-typography`. It could've been moved there, but instead was moved to
a new `bulleted-list` mixin that now became included by both
`.md.md-preview-holder` and `.note-text`.

Since https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5162,
comments have also been wrapped in `.md`, which means we only need to
define these bulleted list styles there!

Similarly, https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10909
added table styling to `.md`, `.note-text`, and `.wiki` through the
`markdown-table` mixin.
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/25666 removed it
from `.note-text`, since all `.note-text` elements already have `.md`
too, and copied some of the styling from this mixin into the
`md-typography` mixin which was used by both `.md` and `.wiki`. As of an
earlier commit in this MR, `.wiki` is gone, which means we only still
need it under `.md`.

Rollback change that adds :not(js-syntax-highlight) pseudo-class
to markdown selectors to fix syntax highlight tables in
MR code suggestions. Removes redundant inclusion of
md-typography mixin as an alternative fix.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/58625

Added stylelint to static-analysis
Updated yarn dependencies
CSS Fixes and rule adoptions of stylelint
Added stylelint-scss
Deduplicated yarn.lock to clear dependencies

First round of advanced stylelint rules

Mainly Vendor prefix updates related to flex

Updates to more webkit specific vendor prefixes

Finished all vendor specific fixes

Moved now 4 rules to warning

Fixed the new scss lint problems

More stylelint adaptions after rebase

Compile highlight CSS separately
Move highlight-specific mixins out of mixins.scss
Rename solarized themes to match theme name as this was a smaller
change than changing all instances to snake_case

Removed the `note-text` class since it conflicted other classes.

Removes old buttons,links and tooltips and uses
the new gitlab-ui components.

Remove jquery.scss; Combine multiple duplicate grays into global gray variables; Remove unused styles in common.scss

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/44024