[1.21.2] Add events fired during framegraph setup

[XFactHD]

This PR adds events during the framegraph setup at the start of level rendering. These allow adding custom passes to the graph and enabling entity outline post-processing without any entities in view having active outlines.
The pre event is fired right after the "clear" pass is set up and the post event is fired right before the graph is executed.

Opening as a draft for now because I'm not totally sure whether the split into pre and post is actually useful or whether the pre event primarily for the outline stuff and people using mixins to precisely inject custom passes between vanilla passes is more suitable.

[neoforged-pr-publishing]

• Publish PR to GitHub Packages

Last commit published: 50547bead8c8305f35da1fe345a91259550d669e.

PR Publishing

The artifacts published by this PR:

• 📦 net.neoforged:testframework:21.3.3-beta-pr-1598-frame_graph_setup_events
• 📦 net.neoforged:neoforge:21.3.3-beta-pr-1598-frame_graph_setup_events

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 #1598' // https://github.com/neoforged/NeoForge/pull/1598
        url 'https://prmaven.neoforged.net/NeoForge/pr1598'
        content {
            includeModule('net.neoforged', 'testframework')
            includeModule('net.neoforged', 'neoforge')
        }
    }
}

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-pr1598.
On Powershell you will need to remove the -L flag from the curl invocation.

mkdir NeoForge-pr1598
cd NeoForge-pr1598
curl -L https://prmaven.neoforged.net/NeoForge/pr1598/net/neoforged/neoforge/21.3.3-beta-pr-1598-frame_graph_setup_events/mdk-pr1598.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.

[neoforged-automation]

@XFactHD, this pull request has conflicts, please resolve them for this PR to move forward.