[Tasklist] Proc macro improvements

[HaronK]

• [x] #145
• [x] #124
• [x] #139
• [x] https://github.com/Limit-Theory-Redux/ltheory/issues/250
• [x] #123
• [ ] Fix Option<&str> as input parameter
• [x] https://github.com/Limit-Theory-Redux/ltheory/issues/243
• [ ] Cleanup COPY_TYPES from types that should not be there: Vec3, Vec4, etc.
• [ ] Add alias parameter (see discussion here https://discord.com/channels/695088786702336000/1001727717848391810/1158504311156912229)
• [ ] Renaming class in the FFI doesn't work if it is used under it's original name in another FFI class
• [ ] Return an error if user is trying to return non-copyable type by value (or do the same trick as with returning string - static storage)
• [ ] Get rid of COPY_TYPES list if possible
• [ ] Resolve all TODOs
• [ ] Automatically generate extensions for methods returning string (example: Engine::get_version())
• [ ] Do not generate Free function and 'Metatype for class instances' section for enum with with_impl = true argument