Add proper eth subscribe support

[jennijuju]

from: #9863 (comment)

• subscribe is not supported
  • The only real way to do this correctly requires a bunch of changes is go-jsonrpc.
    • I'm surprised that what we have today for eth_subscribe works at all
      • It doesn't return the subscription id correctly
      • It doesn't invoke the correct notification on the client
      • The params in the notifications are in the wrong format (array with [id, value] vs object with those)
      • eth_unsubscribe id has nothing to do with the id used by go-jsonrpc when handling the channel
    • To fix this we'll need to add proper support for reverse calls in go-jsonrpc, and add support for object-based parameters
      • Or allow hooking into the raw rpc stream, but that has performance implications
      • Or add support for custom channel logic, but that's about the same amout of work needed for reverse calling, and less flexible
      • Implementing reverse calls is probably 1-2 days, but is that worth it now for proper eth_subscribe support?

[jennijuju]

blocked on filecoin-project/go-jsonrpc#88