Bump polkadot-sdk to 2604.1.0 (#558)

* Bump polkadot-sdk to 2604.1.0

Update workspace dependencies from polkadot-sdk 2604.0.0 to 2604.1.0.

* Register cumulus-pallet-parachain-system v2->v3 migration

The 2604.1.0 bump raises cumulus-pallet-parachain-system on-chain
storage version from 2 to 3 (kills PoVMessagesTracker). Add its
Migration<Runtime> to the Unreleased list in both runtimes so the
try-runtime upgrade check passes.

* Add bulletin-paseo-next-v2 to check migrations

* Bump runtimes spec_version to 1_000_015

Author: bkontur