[1.20.4] Many API Additions

[hammy275]

A 1.20.4 port of #184 . This also adds a couple of new changes:

• Moved isVanillaRenderPass() to the bottom of the file, since its still marked @Beta. Perhaps we want to make a VivecraftRenderingAPI or something, just for organization?
• Added isFirstRenderPass() and getCurrentRenderPass(), as requested.

All features can be tested with this test mod. Note that the test mod itself has only been tested on Fabric, but should work in Forge.

[hammy275]

Rebased onto Multiloader-1.20.4. Haven't tested it, but there were only a handful of merge conflicts with very simple fixes for all of them. Should be good to test with the test mod linked above.

Unrelated, but if it makes life easier, I'm happy to rebase this after #284 is merged.