NIP PRs mostly never get merged and most impls do support it afaik
Discussion
I use multiple filters in a single REQ quite a lot. Some SDKs do this automatically, are we going to break those? Me no like.
We shouldn't merge the PR, relays should continue to support multiple filters. But, having implemented this in coracle recently, it's actually super nice because it encourages callers to split requests by filter, which results in slightly faster response times for each result set.