Add support for the base game's custom shaders

[legoandmars]

It's not feasible to decompile custom shaders such as the posterization shader, which means they're very difficult to use in editor.
YAML shaders might work, but are buggy/unstable and won't work in a build.

I present a new (slightly scuffed) method of using the base game's custom shaders, one that supports:

• Editor
• Editor play mode
• Builds

Here's how it works:

An additional pass is added that uses AssetsTools.NET to extract the compiled shader objects from the game.

After getting these objects, we create a new AssetBundle in-editor using a dummy shader. Once the AssetBundle is compiled, we use AssetsTools.NET to swap out the dummy shader for our base game custom shader, then recompile the AssetBundle.

This will create a seperate AssetBundle for each base game shader in the StreamingAssets/ShaderInjections folder.

These AssetBundle shaders can then be used as normal shaders until one of the following happens:

• You relaunch the editor
• You save a scene in which the materials are present

I have included patches that automatically replace the shader with the correct one when both of these events happen, making the shader look seamless from the perspective of the user.

Problems

I am not 1000% sure well how this works long term, or if there's any stability issues. I haven't run into any big problems, but the only way to know for sure is to have somebody use this in their project while doing complicated tasks for a long period of time.

Runtime/Patches/CustomPassRuntimePatch.cs should probably be replaced with something that happens at project extraction time.

Ideally this would use AssetRipper instead of AssetsTools.NET to avoid adding more dependencies, but I am not super familiar with AssetRipper or how that would be made.

[legoandmars]

more notes:

• The HoloGramShader should work now, but the animation is broken due to a bad reference to the Volume (you can view the animation clip to see what I mean)
• The bee shader could work if we got VisualEffect extraction working, but I'm not sure how realistic that is