Update to bevy 0.12 + redo physics

[jim-works]

This is part 1 of a series of cleanup updates before development starts on the game proper. Part 2 will be improved saving/loading (+ support for block types created in game!). Part 3 will be improved multiplayer.

• Update bevy to 0.12
  • Known issue: shadows are sometimes not rendered based on camera orientation (potentially Directional light shadows disappear when camera is rotated bevyengine/bevy#8645 + Cascaded shadow maps: Fix prepass ortho depth clamping bevyengine/bevy#8877)
• Switch to custom physics system (removed rapier)
• Add interpolation and update transforms in fixedupdate
• Add support for migrations to world db for future breaking changes
• Add movement modes (press F to toggle flight)
• Add fullscreen toggle for F11