Add [x]OrThrow methods

[wyozi]

Adds some shortcut methods to get data/count from a Supabase query. I've added these helpers to a couple of codebases and have found them very useful, so I think they would be useful to have in the library itself as well.

[mmkal]

Somewhat related #494 - although I think both could be useful together. The only difference #494 would make to this is that you'd no longer need the !.