Completely update godot-vrm addon to latest version

[you-win]

The majority of the godot-vrm addon code is actually the code from ~January 2021 and there have been significant updates since then. The application is actually currently able to run off of Godot's 3.x branch but loading .vrm files is broken because of the outdated addon.

After chatting with the V-Sekai team, it looks like my modifications to the addon were unnecessary, so it should be possible to use the godot-vrm addon as a git submodule.

• [ ] update godot-vrm to be a git submodule
• [x] update VRMMappings.gd to pull bone mappings from vrm_meta.gd instead of intercepting the mappings inside of import_vrm.gd. VRMMappings.gd is used for mapping facial blend shapes (e.g. blinking, mouth open, etc) to facial tracking

[you-win]

still waiting on merge from upstream godot-vrm repo

[fire]

What things are requested?

[you-win]

In order to use godot-vrm as a git submodule, the changes from this pr are required.

[fire]

Let's update this issue.

[you-win]

The issue is still technically blocked since the pr hasn't been merged yet + I have several other changes on my local version to work around Resource files losing data after being created (i.e. Resource files from godot-vrm have been changed to Reference and have the duplicate() function manually implemented.

If the pr will never be merged, then both the pr and this issue can be closed

[you-win]

Closing this issue for now, my fork of godot-vrm has diverged fairly heavily. Might open a new issue if a Godot 4 port of openseeface-gd comes around.