Improve equal access behaviors

[Jikoo]

• Add prefix for view-only state
• Add permission nodes for fine-grained control of behavior when accessing

This contains an internal structural change to refactor out duplicate code, and I don't know why I didn't do it this way from the start (Was I just lazy? Was there some error?), so I probably should test pretty extensively. Modern Paper should be fine, but 1.21.4 and below may be indirectly wonky, and Spigot is always a bit of a mess due to the way it's set up. I may also try to make the generics a little less gross.

• Update wiki with new nodes
• Test

Closes #341
Closes #344

[Jikoo]

Oh, another note to self: I left a comment (now in common's OpenSyncMenu) that certain shadowed fields may be removable when 1.21.4 is dropped. It may be a good idea to revisit that as part of this PR, because 1.21.4 already had separate sync process overrides. The current sync restrictions may be Spigot-specific, too.

[Jikoo]

Looking like dropping lower 1.21 versions might be a good idea anyway. When testing on 1.21.4, I got errors about access to the endpoint used to look up players by name being denied. Vanilla commands, too, like /op, not just OI commands. Probably for the next release after the one containing this.

[Jikoo]

Another note: No feedback when inventory fails to open due to lack of access. May want to move access check into generic command's permission checks to impose fewer restrictions on other plugins' behavior if they try to open OI's views.

I think this needs a modification of the method signature, which is why I didn't do it in the first place.