feat(bms,ladfile_builder): introduce app global instance registry and export them in ladfile_builder

[makspll]

Summary

• Adds AppScriptGlobalRegistry
• Pushes responsibility of registering globals up to BMS core
• Does not cover all globals, as entity, world and script_id have more complex requirements, these will be taken care of later, probably by being moved to actual functions (which will also avoid needlessly allocating entities)
• Makes ladfile_builder export globals to the ladfile format as defined earlier
• This is now visible in the global docs
• Also adds script_globals derive macro, but I am not sure how useful that's going to be

addresses: #322