feat(p2p)!: remove conngater dependency

[walldiss]

libp2p conngater is exact type and not an interface, which makes it impossible to modify or mock its functionality on client side. Replaces libp2p conngater dependency with callback func, to allow easy mocking for clients.

Required by https://github.com/celestiaorg/celestia-node/issues/2702 to provided conngater with white list instead of basic one.