Organize and feature-gate FASTSim-2 compatibility code

[kylecarow]

• create compat mod and feature
  • feature gate dependencies that are needed with updated Cargo.lock
    • something about running cargo update in fastsim-3 with the existing setup causes failure on some platforms, this is the fix (rather than never updating Cargo.lock)
• move all compatibility code to compat
  • from_f2_file still needs to live in the impl with other pymethods, not a huge deal
  • remove all remaining references to fastsim2 in fastsim-3 outside of compat::fastsim2
• compat/assets folder to organize any f2 assets (e.g. vehicle files)
  • include_dir instead of include_str
  • move f2-*.yaml loose files to compat/assets
• refactor code that previously loaded fastsim-2 models to convert to fastsim-3 (e.g. mock_veh functions)
  • these now just load from resources
• remove cal_and_val linkage to simdrivelabel
  • PHEV file just lives in fastsim-core now which makes more sense
• add explicit test coverage for f2 to f3 vehicle conversion