Process instruction with observer

[rustopian]

[WIP] more docs etc. incoming shortly, plus an evaluation of any overlap with #161

Problem

Callers can have some difficulty retrieving all information about a processed mollusk instruction or instruction chain. In particular, updating tests to compare CUs, account states, and results can be a bit tedious.

Solution

Allow an observer to be passed in to the new with_observer wrapper functions. This observer is handed all the relevant information so that the caller's testing setup can easily process it.

Context

This is part of a simple solution to provide developers an easy #[compare_programs] attribute, which makes a test compare CUs and check byte-for-byte parity of accounts, data, and instruction results, across any arbitrary number of versions of a program.

[buffalojoec]

Hey, does this do something different than the InvocationInspectCallback?

mollusk/harness/src/lib.rs

Lines 494 to 498 in 88d56ab

	/// The callback which can be used to inspect invoke_context
	/// and extract low-level information such as bpf traces, transaction
	/// context, detailed timings, etc.
	#[cfg(feature = "invocation-inspect-callback")]
	pub invocation_inspect_callback: Box<dyn InvocationInspectCallback>,

mollusk/harness/src/lib.rs

Lines 748 to 750 in 88d56ab

	#[cfg(feature = "invocation-inspect-callback")]
	self.invocation_inspect_callback
	.after_invocation(&invoke_context);