In investigating #7947 it has become clear that the storage component of go-git repositories needs closing.

This PR adds this Close function and adds the Close functions as necessary.

In TransferOwnership the ctx.Repo.GitRepo is closed if it is open to help prevent the risk of multiple open files.

Fixes #7947

* Initial implementation for git statistics in Activity tab

* Create top user by commit count endpoint

* Add UI and update src-d/go-git dependency

* Add coloring

* Fix typo

* Move git activity stats data extraction to git module

* Fix message

* Add git code stats test

Signed-off-by: Lauris Bukšis-Haberkorns <lauris@nix.lv>

* Integration test for activity page

* Small code refactoring for acitvity page

* Move activity stats calculation logic to model

* Add Activity page to repository

* Add request data for activity

* Add issue data for activity

* Add user unit right checks

* Add releases to activity

* Log repository unit loading error