[1.21.3] Expose vanilla model generators for modded usages

[ApexModder]

This PR allows modders to make use of the vanilla model generators and all the helpers/utilities that come with them.
This is done by adding methods which modders must override in each of the main data providers, failing to override these methods will result in vanilla models being generated.

Various ResourceLocation.withDefaultNamespace calls have also been patched to now call ResourceLocation.parse, this is to support passing in paths with modded namespaces.

With 1.21.4 and all of its model changes, this is intended as a stepping point towards using the vanilla generators. Rather than having to patch and potentially rewrite ours to support all these changes.

TODO

• Add ExistingFileHelper support, validate referenced textures and parent models exist
• Expand ModelBuilder to pass its output to ItemModelOutput, allowing modders to build custom models
• Support our RenderType and face data extensions when using template models
  • Unsure if mutating face data is possible using model templates
• Generate texture animation mcmeta files?
• Validate that added ATs are still needed after recent changes.

_{Original conversation can be found in NeoCord}

[neoforged-pr-publishing]

• Publish PR to GitHub Packages

Last commit published: 937460d091f56548d8fdb84b6fc03bcf5b9719ba.

PR Publishing

The artifacts published by this PR:

• 📦 net.neoforged:neoforge:21.3.73-beta-pr-1696-pr-vanilla-data-gen
• 📦 net.neoforged:testframework:21.3.73-beta-pr-1696-pr-vanilla-data-gen

Repository Declaration

In order to use the artifacts published by the PR, add the following repository to your buildscript:

repositories {
    maven {
        name 'Maven for PR #1696' // https://github.com/neoforged/NeoForge/pull/1696
        url 'https://prmaven.neoforged.net/NeoForge/pr1696'
        content {
            includeModule('net.neoforged', 'neoforge')
            includeModule('net.neoforged', 'testframework')
        }
    }
}

MDK installation

In order to setup a MDK using the latest PR version, run the following commands in a terminal.
The script works on both *nix and Windows as long as you have the JDK bin folder on the path.
The script will clone the MDK in a folder named NeoForge-pr1696.
On Powershell you will need to remove the -L flag from the curl invocation.

mkdir NeoForge-pr1696
cd NeoForge-pr1696
curl -L https://prmaven.neoforged.net/NeoForge/pr1696/net/neoforged/neoforge/21.3.73-beta-pr-1696-pr-vanilla-data-gen/mdk-pr1696.zip -o mdk.zip
jar xf mdk.zip
rm mdk.zip || del mdk.zip

To test a production environment, you can download the installer from here.