multi: send P2TR addrs by default for co-op close, add new `option_any_segwit` feature bit
In this commit, we implement the new option_any_segwit feature bit which enables us to start sending P2TR addresses for co-op closes as well as for upfront shutdown addresses. Along the way, we tighten up our validation a bit to only allow segwit v0 and v1 addresses.
The refactoring I did in #6770 should make it easier to write unit tests for this change as well.
@roasbeef, remember to re-request review from reviewers when ready
Ok, I think this is g2g now: just pushed up fixes, a new unit test, and also an itest to make sure negotiation works e2e.
Proper version should be pushed up now (w/o the commit that bumps the Go version).