contracts: add direct contract backend

[taratorio]

relates to #13383
takes a chunk of changes out of bigger shutter PR #13553 in which we collect data from various shutter smart contracts

context on this PR:

• smart contracts objects generated by abigen rely on bind.ContractBackend in order to be used
• we currently do not have an implementation of that interface in Erigon (apart from SimulatedBackend which is used in testing - inherited from Geth)
• in this PR im adding an implementation of ContractBackend which uses the EthApi jsonrpc object and directly calls it instead of going via http rpc and/or websocket (for log update subscriptions) - this is analogous to how we have direct and remote grpc clients for our grpc-based components
• ive also wired the new contract backend to the shutter pool - this will be used in a subsequent PR (check the aforementioned PR shutter: collect data from smart contracts #13553 for usages)

note that this is needed also for @shohamc1 's work for native AA which is why it will be good to merge it in main