build: loom-adapter → loom-back-compat

[MattSturgeon]

Migrate from our own implementation of loom-adapter to loom-back-compat. Our implementation was originally based on an early draft of loom-back-compat shared by @kikugie on discord.

Doesn't seem to be working for me locally. loom-back-compat is attempting to add fabric-loom to the buildscript classpath and Gradle complains that no repositories are configured. However we do have the fabric repo configured.

A problem occurred configuring project ':cloth-config'.
> Could not resolve all dependencies for configuration 'classpath'.
   > Cannot resolve external dependency net.fabricmc.fabric-loom:net.fabricmc.fabric-loom.gradle.plugin:1.15-SNAPSHOT because no repositories are defined.
     Required by:
         buildscript of project ':cloth-config'
   > Cannot resolve external dependency net.fabricmc.fabric-loom-remap:net.fabricmc.fabric-loom-remap.gradle.plugin:1.15-SNAPSHOT because no repositories are defined.
     Required by:
         buildscript of project ':cloth-config'

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Pros:

• One less thing to maintain here

Cons:

• Loom version cannot be managed by the version catalog
  • It must use either a property or a settings DSL