Document Crawlspaces

[engineer124]

A followup to BgCamInfo. Crawlspaces are primarily covered by 4 systems:

• camera
• player
• bgcheck
• onepointdemo

This documents crawlspaces across these different systems. Two comments to add on:

1. Camera is cursed with reused temps for different variables. It was decided a while ago to try and use macros to deal with this in Camera_Subj4 but I feel I've grown less fond of this approach over time. I've left it in for now, but open to suggestions/ideas
2. The data for crawlspaces in camera_data.c is very strange and contains what appears to be unused data. This is likely due to devs using it for one implementation, but dropping it for another. It's hard to say for certain. See this PR for more info: https://github.com/zeldaret/oot/pull/1225