WIP: 3D Models

[lpenguin]

This is work-in-progress state of 3D models branch. This PR uses custom rusty-vangers branch: https://github.com/lpenguin/vange-rs/tree/ff-set-visible

Current state:

• [x] Rust backend models functions
• [x] Basic hooks in the main code: model initialization, model instance creation, model instance destruction
• [ ] Incomplete: Mechous weapon position
• [ ] Solve coordinate systems conflict in main code (left-handed) and rusty-vangers (right-handed)
• [ ] Decouple game logic from the rendering logic: we determine mechous water level from per-pixel rendering. See https://github.com/KranX/Vangers/pull/577/files#diff-d7665497c39e5e103a915ab4e4cf2ed9b0f880f8831d2cc0b888be13213b1bdcR301
• [ ] Adjust mechous perspective scaling
• [ ] Solve items visibility issues
• [ ] Solve vector math duplicated code: main code and renderer subproject: move all mod-related code parts into new libvangers project
• [ ] Solve architectural issues: higher level classes for graphics objects