Implement oracle factories

[totomanov]

This PR implements the following:

• FeedRegistry.sol, a Governable contract that holds a mapping (base,quote) -> FeedIdentifier.
• FeedIdentifier.sol, a library that wraps address/bytes32 in the same data type. This is necessary because the registry for Chainlink and Chronicle stores addresses, while the registry for Pyth and Redstone stores bytes32s.
• `OracleFactory.sol, a common interface for oracle factories.
• BaseAdapterFactory.sol, an abstract base contract for oracle factories.
• 4 adapter factories for Chainlink, Chronicle, Pyth and Redstone
• OracleMultiFactory.sol, a Governable meta-factory. It maintains a mapping of enabled factories and records all deployed oracles.
• Tests for all of the above. Some improvements (mostly refactoring) to existing tests

IOracleFactory

interface IOracleFactory {
    struct DeploymentInfo {
        address deployer;
        uint48 deployedAt;
    }
    function deploy(address base, address quote, bytes calldata extraData) external returns (address);
    function deployments(address oracle) external view returns (address, uint48);
}

• extraData contains abi-encoded extra deployment parameters e.g. maxStaleness.

OracleMultiFactory

• governor can enable and disabled an IOracleFactory
• governor can set a singleton oracle e.g. LidoOracle to the deployments
• user/product line can deploy an oracle through the allowed factories
• user/product line can verify that an oracle is deployed by one of the enabled factories

[totomanov]

Closing for now. Factories are out of scope for this repo.