Retool to Essential Loom

[Elephant1214]

Retool to Essential Loom, supporting up to Fabric 1.21.1 and Forge 1.21, and now requiring Java 21.

Things to note

• A Java 21 JDK is REQUIRED, not optional
• 1.12.2 runs MUST USE JAVA 8 or they won't work
• Tasks on subprojects must be run through the main project using gradlew :subprojectName:task

Problems

• Resources are not shaded into 1.12.2 and 1.16.5 projects when run in an IDE for some reason
• No way to automatically update version numbers (yet)
• Jar names are probably not to Don's liking, but this can be fixed easily
• Access Transformer AND Access Widener required for modern Forge, but apparently Essential Loom can convert these itself on the fly (?)

[slava110]

Note that for 1.12.2 forge version will be downgraded from 14.23.5.2860 to 14.23.5.2840. Though, I don't think there's a lot of important changes for dev environment between these versions

[Elephant1214]

Note that for 1.12.2 forge version will be downgraded from 14.23.5.2860 to 14.23.5.2840. Though, I don't think there's a lot of important changes for dev environment between these versions

No difference for MTS. All I've found is that Mixin has a few problems with mappings, but using UniMix fixes them.