op-supervisor: Create logdb for each chain

[ajsutton]

Description

Updates op-supervisor so that it creates a logdb database for each chain it monitors. Pretty much entirely just wiring code and moving things around to make the chain ID available as needed. The NewBackend function is getting a bit complex for my liking but going with it for now as it is just the constructor so having wiring code in there isn't too bad and I'm keen to actually get a minimal pipeline hooked up end to end before trying to guess exactly where things will land.

Metadata

• Fixes Interop: op-supervisor: Create log db for each chain #11023

[protolambda]

LGTM.

For later updates I suggest we add a type ChainID uint256.Int however; then we can attach utils to the chainID, and use it as map-key (uint256.Int is an array of 4 uint64, safe to use as key, unlike *big.Int). And then we can do map[ChainID]*db.DB.