Add support for pure-binary grease pencil line art files

[DJLevel3]

Pretty much as described in the title, this improves line-art loading and parsing performance immensely at the expense of making the files non-human-readable (though they were pretty unreadable before, lmao) and deprecates the JSON format (though preserving the format's useability).

[DJLevel3]

This PR also adds support for Blender 4.2+ via a second, identical version of the Blender addon that has the proper blender_manifest.toml alongside the script.

[DJLevel3]

I'll have to redo these changes as they're not compatible with the LuaJIT changes in #259. Closing for now, I'll get back to it once things are finalized with LuaJIT.