- Project listing icons now use the `text-secondary` class
- Group listing icons now use the `text-secondary` class
  - Unnecessary CSS was removed from groups.scss as a result

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

- Makes activity dropdown and resolved counter smaller
- Uses grid for spacing
- Removes scrolling on MR tabs

- Avatar, group name, and group description now left-aligned
- Notification setting and "New project" CTA right-aligned
  with group avatar and name
- Leave group / request access now a link next to the 'Group'
  label below the group name
- Notification setting label removed in favor of icons
  - Tooltip added to indicate notification setting
- Search option moved inside table header next to "Sort by"

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

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

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

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

* Reset p bottom margin for group lists to fix vertical alignment
* Remove double border for group lists to be consistent with project
lists

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

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