Implement structural checkers for proofs

[tothtamas28]

This would enable us to verify foundry_prove test results structurally, as opposed to comparing foundry_show output to an expected string, which is very brittle.

[ehildenb]

What we really want to test is something like:

• Same graph structure overall.
• Same depth of each basic block.
• Same branching conditions.
• Same end conditions.
• Roughly same configuration each state.

Comparing the string output roughly approximates that, but doing it structurally would be better. Maybe we store the actual KCFGs and have an intentional way of diffing them (or the APRProof)?

[tothtamas28]

Renamed the PR and edited the description to better reflect this goal.