better savestates

[briaguya-ai]

as of #3095 we can basically treat savestates as an unimplemented feature, this can be used to track progress on implementing savestates in a way that better aligns with player expectations coming from emulator/gz

there are a few open savestate issues, plus the lack of ability to load states after quitting/opening the game seems to confuse people all the time

• Load state bug #1048
• Save states messing with scene #341
• Fishing rod save/load state bug #389
• Truth spinner in Shadow temple doesn't get state restored properly via savestates #1189

i might have missed a few, i'll add them if i find them

[jbodner09]

We also should probably do a complete scrub of all instance variables that have been added since savestates were implemented since they're likely missing from them.