figure out minimal avs contract interface to make avs-sync work

[samlaf]

Currently avs-sync relies on many contracts in https://github.com/Layr-Labs/eigenlayer-middleware
I'm too lazy to list them all right now but OperatorStateRetriever is definitely needed, as well as some functions in RegistryCoordinator (getQuorumCount for eg), and possibly some in StakeRegistry, but not sure.

We will need to make versions of avs-sync that work for teams who write their own avs registry contracts.
Would be good to find the exact interface requirements of the current implementation and see if we can minimize it.