[wip] build actor tool (#3266)

This does a couple of things:

- The `custom_levels` folder was renamed to `custom_assets` and contains
`levels`, `models` and `texture_replacements` folders for Jak 1, 2 and 3
in order to keep everything regarding custom stuff in one place.
- With this, texture replacements now use separate folders for all games
- A build actor tool was added that generates art groups for custom
actors
- Custom levels can now specify what custom models from the `models`
folder they want to import, this will add them to the level's FR3.
- A `test-zone-obs.gc` file was added, containing a `test-actor` process
that uses a custom model as an example.

The build actor tool is still very WIP, the joints and the default
animation are hardcoded, but it allows for importing any GLB file as a
merc model.

.github/scripts/releases/extract_build_unix.sh

@@ -32,4 +32,4 @@ cp -r $SOURCE/decompiler/config $DEST/data/decompiler/
 cp -r $SOURCE/goal_src $DEST/data
 cp -r $SOURCE/game/assets $DEST/data/game/
 cp -r $SOURCE/game/graphics/opengl_renderer/shaders $DEST/data/game/graphics/opengl_renderer
-cp -r $SOURCE/custom_levels $DEST/data
+cp -r $SOURCE/custom_assets $DEST/data

.github/scripts/releases/extract_build_windows.sh

@@ -24,4 +24,4 @@ cp -r $SOURCE/decompiler/config $DEST/data/decompiler/
 cp -r $SOURCE/goal_src $DEST/data
 cp -r $SOURCE/game/assets $DEST/data/game/
 cp -r $SOURCE/game/graphics/opengl_renderer/shaders $DEST/data/game/graphics/opengl_renderer
-cp -r $SOURCE/custom_levels $DEST/data
+cp -r $SOURCE/custom_assets $DEST/data