Add support for more block tags (e.g. finalized, safe) in Filecoin.EthGetLogs

[sudo-shashank]

Ethereum supports more block tags than just "latest" and "earliest" (e.g. "finalized" and "safe"), but lotus does not handle these as of now.

This issue tracks adding support for these block tags in the future once requirements and use-cases are better defined.

Ref: https://github.com/filecoin-project/lotus/blob/df9e10ef0af35613c65178a5740fde37c03efc8e/node/impl/eth/events.go#L576-L585