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

Adds CHANGELOG entry

Adds MR ID to CHANGELOG entry

* Simplify code around group parent access check
* Rename 'Nested groups' to 'Subgroups' tab at group#show page
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

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

This adds counters for build artifacts and LFS objects, and moves
the preexisting repository_size and commit_count from the projects
table into a new project_statistics table.

The counters are displayed in the administration area for projects
and groups, and also available through the API for admins (on */all)
and normal users (on */owned)

The statistics are updated through ProjectCacheWorker, which can now
do more granular updates with the new :statistics argument.

This ports some code over from EE to reduce conflicts

Added new spec step

Added empty state to dashboard

Split empty and filtered empty states

Moved empty_state icons into their own folder and DRY up empty state html

Fixed failing spec

Added to groups page

Review changes

Signed-off-by: NRémy Coutable <remy@rymai.me>