Port to 1.21 (#511)

* 1.21-pre1

* progress

* fix MixinGameRenderer

* update the access widener

* pass removal reason in the player respawn event

* Update MixinGameRenderer.java

* fix more mixins

* fix more 1.21 stuff

* Update TestRegistries.java

* remove enchantments (it's data driven)

* rename 1.20.6 files to 1.21

* update to 1.21-pre4

* lol

* fix neoforge

* Finish port to 1.21

---------

Co-authored-by: shedaniel <daniel@shedaniel.me>

.github/workflows/1.21_pr.yml

@@ -7,7 +7,7 @@ on:
       - '**.properties'
       - '**/src/**'
     branches:
-      - "1.20.6"
+      - "1.21"
     types: [ opened, synchronize, reopened ]
 jobs:
   validate-gradle:

.github/workflows/1.21_push.yml

@@ -8,7 +8,7 @@ on:
       - '**/src/**'
       - '.github/**'
     branches:
-      - "1.20.6"
+      - "1.21"
   workflow_dispatch:
     inputs:
       norelease: