Allow choosing "Must be blocked by all the blocklists I'm subscribed to"

[SoniEx2]

Currently when you subscribe to multiple blocklists it only has the effect of "Block ppl who... are blocked by any one of the blocklists I'm subscribed to" and I'd like to be able to switch it to "Block ppl who... are blocked by all of the blocklists I'm subscribed to".

This would make blocktogether a lot better as I wouldn't have to trust everyone I subscribe to. This basically completely eliminates personal blocks from being picked up by blocktogether, so that only community threats actually get blocked. Also provides a "cushion" for bias and bigotry where if one of the lists I subscribe to start blocking based on bias and bigotry, it won't automatically block those ppl unless the other lists also do the same.