refactor: add a interface for chain poller

[fyInALT]

In currently, the finality provider 's manger and instance use a fixed chain poller to fetch block infos from consumer chain, but for different consumer chain, the poller 's implment maybe very different.

Now the ChainPoller struct can work well for eth layer2 or op based layer2, but can not support other layer2 like orbit or zksync, so if we make a service to support orbit based consumer chain, we can not reuse the finality-provider 's code.

So we add a interface for chain poller, it can allow other service implment it 's spec poller for other chain. because the manager will create instance in runtime, so we add a chain poller factory interface as a creator.

TODO: in future we can add a mock for chain poller to test some case like consumer chain block reorg.