This method, #route_not_found, is executed as the final fallback for
unrecognized routes (as the name might imply.) We want to avoid
`#authenticate_user!` when calling `#route_not_found`;
`#authenticate_user!` can, depending on the request format, return a 401
instead of redirecting to a login page. This opens a subtle security
exploit where anonymous users will receive a 401 response when
attempting to access a private repo, while a recognized user will
receive a 404, exposing the existence of the private, hidden repo.

Prefer `json_response` where applicable.

Previously the Housekeeping button and API would use the counter of last
pushes to determine whether to do a full garbage collection, or whether
to do one of the less comprehensive tasks: a full repack, incremental
pack, or ref pack. This was confusing behavior, since a project owner
might have to click the button dozens of times before a full GC would be
initiated.

This commit forces a full GC each time this is initiated. Note that the
`ExclusiveLease` in `HousekeepingService` prevents users from clicking
on the button more than once a day.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/63349

Adds frozen string to the following:

* spec/bin/**/*.rb
* spec/config/**/*.rb
* spec/controllers/**/*.rb

xref https://gitlab.com/gitlab-org/gitlab-ce/issues/59758

Move Contribution Analytics related spec in spec/features/groups/group_page_with_external_authorization_service_spec to EE

This reverts merge request !26823

This reduces a handful of duplicate FindCommit calls while viewing the
projects and commits pages.

Move Contribution Analytics related spec in spec/features/groups/group_page_with_external_authorization_service_spec to EE