## Description
This cleans up how synonyms are calculated, and adds a reverse mapping from pseudo keys to the real keys they are synonyms of.
Updates the `layout_goals.json` to include the "Space" key, since that was added in the engine without updating the generation configuration.
The (new, not yet used) code gen for iOS was setting up a std::map from key codes to logical and physical key codes, but it was using uint32_t, which isn't big enough to hold the Flutter key codes.
Also, iOS needs to be able to filter out function keys, so I added a function key set.