New combined JSON config proposal

[ComplexPlane]

Proposal/prototype for a new combined JSON config for wsmod. All per-stage configuration (ID, name, theme/music ID, time limit, warp goal jump distance, etc.) is grouped by stage and organized in story/challenge layout sections. See default-config.json for a mostly complete configuration of vanilla SMB2.

Config parsing is working at both the JSON and config format level, but implementing the story/challenge configs in-game is still TODO.

I'm using ArduinoJson to parse the config which is meant to be a small code/memory size and ergonomic JSON parser. One issue is that if there's a JSON parse error you can't retrieve a error location/message, but the library's simple enough it looks eas y to add at least a parse error location if needed. I have an error suggesting people use an editor like VSCode to look for JSON parse errors as well, since it's a standard language and all. On the contrary, errors parsing the config format itself are much better IMO.

Also, the plan for memory management is to do all parse-related allocations in a separate heap allocated in a block at the end of the main heap which is freed after all init_main_loop() functions are called. The idea is patches read from config and do their thing, copying from the parse heap and/or writing to the game's memory under the assumption the parse heap will be freed. A separate heap prevents heap fragmentation.