Add publicly accessible caching keys for supabase-js queries

Right now, making use of the PostgREST functionality with a library like @tanstack/react-query means writing your own cache keys or using the implementation detail of .url. Obviously neither is ideal. It would be better if the Supabase library instead exposed some kind of deterministic cacheKey property that had info for a few levels of specificity, similar to how react-query caching keys allow very broad or very specific cache clearing.