`Time#to_date` just takes the (timezone-less) year, date, and month, and
creates a new date from that. Because the commits in the list are
grouped by date, rather than chunked when the date changes, a commit can
be shown in the wrong order if its CommitDate has a timezone-less date
that's different to other commits around it.

Convert all CommitDates to the server timezone before grouping, as that
will at least produce consistent results. Users can still see a
timestamp on the commit that doesn't match the date it's grouped under,
because the timestamp shown uses the user's local timezone, and the
grouping uses the server's timezone, but that was an issue anyway.

Log to application.log when an admin starts and stops impersonating a user

Closes gitlab-org/gitlab-ee#536

See merge request !4028

Merge request widget displays TeamCity build state and code coverage correctly again

## What does this MR do?
This MR contains a fix for a regression introduced in `8.7`. In former version, the TeamCity build status was always displayed correctly. In `8.7` the build state is still checked, but the UI is not updated correctly any longer.

## Are there points in the code the reviewer needs to double check?
The changes are quite simple, so please simply double check them.

## Why was this MR needed?
This MR is needed to make the TeamCity build status working again.

## What are the relevant issue numbers?
#17080 

See merge request !3998

Use `number_to_human_size` helper to show repository size

This will intelligently format large repository sizes in GBs (or,
shudder, TBs).

Also, removes `rescue` clause from `repository_size` helper.
The repository size has since become calculated (and cached)
more intelligently, and this should no longer be necessary.

See merge request !4047

The repository size has since become calculated (and cached) more
intelligently, and this should no longer be necessary.

This will intelligently format large repository sizes in GBs (or,
shudder, TBs).

Sanitize repo paths in new project error message

Closes #17243

See merge request !4029

Closes #17243