Treat different UNIX destinations like different origins

It seems that

1. `unix:` -> `http:` works
2. `unix:` -> `unix:` works
3. `http:` -> `unix:` does not work
4. `unix:` -> `http:` -> `unix:` does not work

2 can leak sensitive headers if the socket path is not the same. For example `http://unix/foo:/` -> `http://unix/bar:/`.

_Originally posted by @lpinca in https://github.com/sindresorhus/got/issues/2047#issuecomment-1170430123_