[2.2.2] ship floatation logic updates and flying fixes

[zolantris]

changelog

• add some custom colliders for convex meshes that need concave collisions (all of the curved hulls get this, mesh colliders do not work well without this)
• swap to CustomFixedUpdate and patch valheim's custom updater, should
  make client updates more stable. Applies to VehicleMovementController and VehiclePiecesController update, fixedupdate, lateupdate
• Add custom height support for vehicle floatation, vehicles can be changed for height between -20 and 20
• Add flight mechanics so vehicles can now fly and ascend descend much
  faster. This requires convex meshes for hulls though.
• Experimentally fix player jitter for floating boats (but may not work as well in some cases).
• Jitter fix is enabled for all clients when flying. This fixes a ton of issues for flight stuttering.