refactor: use Pion's `SetIPFilter` instead of our `StripLocalAddresses`

SetIPFilter was recently added to Pion.

I'm not sure if this gives actual benefits, but to me it seems better if Pion would filter out addresses by itself, instead of us only stripping them off when sending the offer/answer (see 0fae4ee8, 1867f895, #19026 (closed)). It might also solve the problem (if it's a problem) where if a client sends local addresses in its offer, the proxy will try to connect to these local addresses.

Also while we're at it, need to check whether it can be a proper way to solve #40108 (closed).