interop: Bidirectional RPC For Owned Nodes

[axelKingsley]

From this document: https://github.com/ethereum-optimism/design-docs/pull/171/files

Decomposed into: https://www.notion.so/oplabs/tasks-to-make-150f153ee162809e981ac7d30c0bfae2?showMoveTo=true&saveParent=true

What

The Supervisor will be dialing into nodes which it will be driving. When it does such, the connection should be established in a bidirectional way so the two sides may exchange calls with tight coupling

How

Here are some implementation notes:

• Supervisor does the dial, is client. OP Node receives the connection, is server.
• Want to only keep the one connection Supervisor→OP-Node
• Supervisor can attach a server interface during the call to the OP Node
  • OP Node needs to know how to work with the returning API handles
  • example of attaching server to the client connection: https://github.com/ethereum-optimism/op-geth/blob/15fb0dcc6732f3b04f8d3b13e309afd723364ba5/rpc/client.go#L279

Definition of done:

• Supervisor can dial into Nodes and the two can share back and forth API calls.
• Call is authenticated
• Bidirectional RPC is established only for "Owned Node" configured Nodes