Gold Image Testing Epic

We used to have a central server containing gold images to have some graphics unit tests run again.

Now being opensource, this is quite impractical:

• Difficult to setup (not good, we want people to easily run tests by themselves)
• Would need lot of additional work (server was really rudimentary and working with file shares)
• Security issues (if we give access to this server, who are we allowing to update gold?)
• Hardware differences (we can't expect pixel perfect matches)
• Since images are stored externally, it has to be versioned manually and can easily conflict in case of merges.

The idea is now to commit those images as part of the repository, thus requiring no further setup.
Tests will be allowed to have small differences (due to GPU differences).

This work is partially started but still need further work (allow small differences, make it work on all platforms, etc...)

Start by locating the existing graphics unit tests and their gold-image inputs, then review how the external server is used. Define repository-owned image storage, tolerance for GPU differences, and platform coverage. Done means the tests run without additional server setup and accept small hardware-related differences across platforms.