Fix failure to recompute frames in mixins involving mixin-generated classes in stack frames

[lukebemish]

Fixes #434

In certain scenarios frame recomputation of Mixin classes needs to see the superclass of a class mixin generates. However, mixin-generated classes (as well as normal mixin classes) themselves may need frame computation, so that transform cannot be placed before neoforge:computing_frames! (Basically, a given class processor can either have the ability to have its changes be counted for frame computing, or can request computing itself. This is to avoid circularity).

I fix this through a few changes:

• Make a new class processor, neoforge:mixin_frame_context, responsible for making any mixin changes that will affect frame computation
• Move the bytecode capture point used by mixin to look up class hierarchy to this point (this is necessary to avoid circularity)
• neoforge:mixin_frame_context runs generateClass on classes-to-be-generated on a copy of the received class node, then copies over any changes in super type to the actual classnode.This occurs before neoforge:computing_frames
• neoforge:mixin runs generateClass to properly generate the class normally, later, as before.

Basically: I apply the changes in super type earlier by re-running the generator. Generators are safe to re-run -- FML already did that in FMLClassBytecodeProvider. The capture point has to be moved earlier because generators could request stuff from the mixin service, including looking up class info; I suspect this will not have any interesting effects in practice.

[neoforged-pr-publishing]

• Publish PR to GitHub Packages

Last commit published: b0f19ccdef7badb7f40625d9f34c07397ac5f5b0 - version: 11.0.21-pr-435-fix-mixin-frame-computing

PR Publishing

The artifacts published by this PR:

• 📦 net.neoforged.fancymodloader:earlydisplay:11.0.21-pr-435-fix-mixin-frame-computing
• 📦 net.neoforged.fancymodloader:junit-fml:11.0.21-pr-435-fix-mixin-frame-computing
• 📦 net.neoforged.fancymodloader:loader:11.0.21-pr-435-fix-mixin-frame-computing

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 #435" // https://github.com/neoforged/FancyModLoader/pull/435
        url = uri("https://prmaven.neoforged.net/FancyModLoader/pr435")
        content {
            includeModule("net.neoforged.fancymodloader", "earlydisplay")
            includeModule("net.neoforged.fancymodloader", "junit-fml")
            includeModule("net.neoforged.fancymodloader", "loader")
        }
    }
}

[lukebemish]

This PR also includes a test replicating #434; this test will fail without the changes from this PR.