Brainstorming: support for getMappingSlotAt, getMappingLength and getMappingKeyAndParentOf

[bsamuels453]

We had to spend a ton of time re-creating the state machine for a recent invariant project because it held internal state that our fuzzing harness couldn't directly access.

I don't know which cheatcodes are used to allow these foundry functions to work, but I'm curious what the cost would be to add them to medusa:

• getMappingSlotAt
• getMappingLength
• getMappingKeyAndParentOf

Basically a bunch of StdStorage.sol features would be incredible helpful for dealing with protocols with a lot of hidden internal state.

What would the cost of this support be?

[0xalpharush]

For now, I would just use slither-read-storage and vm.load bc we may need to rethink how we're doing cheatcodes given how many issues we've had opened about them recently