Create Rendering "unit" tests

[Geokureli]

I don't think there's a good way to automatically verify rendering working on github actions, but there should be some gauntlet of tests that people should have to manually verify on various targets with various compiler flags (FLX_RENDER_TRIANGLES/QUADS and FlxG.renderBlit/Tile)

TODO

• Make a checklist of things to test, look back at all previous rendering bugs
• Add the project "rendering" to tests