Add `startPrank` support for `tx.origin` and `delegateCall`

[Xenomega]

The PR #594 introduced basic startPrank support, allowing msg.sender to be spoofed.

The tx.origin spoofing and delegateCall flag are not currently supported. Introducing these changes isn't incredibly difficult, but our code did not have access to the relevant unexposed objects in medusa-geth (see PR for more details).

We suspected we would first aim to rewrite the tracer architecture to better wrap duplicative operations (call frame tracking, revert tracking, hooks, etc). I believe after doing that and revisiting what we'd like to expose more deliberately in medusa-geth, adding support for new cheat code additions should be less cumbersome.