Apparently, it's safe to use Unity objects as keys in HashMaps, and doing
so actually fixes some edge cases where assets are recreated as a new C# object.
* chore: rearrange package structure to have the package at the root
* ci: update CI workflows
* ci: fixing workflow bugs
* ci: recurse building .zip package
* ci: more fixes
* ci: add back in the nadena.dev VPM repo
* ci: fix tests
