feat(forge): invariant tests

[brockelmore]

Adds invariant tests.

creates a strategy for selecting a contract from identified contracts, and a strategy for fuzzing the input params. If the call succeeds, check all the invariants in the contract (as defined by invariant prefix to a public function).

TODO:

• multiple rounds of calls (currently only does 1 call)
• function selector strategy currently never grabs index 0 it seems
• update identified contracts after each call (instead of just after setup)
• utilize the calldata strategy in fuzz_dict branch for state lifting
• add state lifting in invariant fuzzes
• add return data & input data into state lift dictionary

[gakonst]

superseded by #1572