Add `rpc` cheatcode: integrate cast rpc as cheatcode

[mattsse]

Component

Forge

Describe the feature you would like

ref #2051
cast rpc allows sending rpc requests like cast rpc eth_getBalance "0xa0ee7a142d267c1f36714e4a8f75612f20a79720" "latest"

it'd be useful to have this as general purpose cheatcode and also have some dedicated helper functions for eg. anvil_impersonateAccount

perhaps we can move this to a new Rpc Interface contract, wdyt @mds1 ?

Additional context

No response

[mds1]

Yea a vm.rpc cheat seems useful, in the past I've used ffi to deal tokens on anvil as part of a forge script but this would definitely be more convenient. Two questions:

1. What would be the UX? vm.rpc(string memory urlOrAlias, string memory method, string memory params)? You'd have to format the JSON string manually which is a bit clunky but not terrible.
2. Should this be disabled by default?

[mattsse]

an array of strings is probably sufficient, same as cast rpc works rn.

since this is POST I think we'd need another permission for this

[Tudmotu]

Henlo, is there any way I can help implement this?

[sam-goldman]

Would this cheatcode work with the in-process node? It'd be useful to call eth_estimateGas without needing to spin up a standalone Anvil node (ref #6590). I'm not familiar with Foundry's internals so I don't know if this is feasible :)

[Tudmotu]

@sam-goldman I believe this cheatcode was actually implemented but not documented:
https://github.com/foundry-rs/foundry/blob/master/crates/cheatcodes/src/evm/fork.rs#L221

Did not try it out myself yet.

[Evalir]

Correct @Tudmotu — this is implemented, just undocumented. I'd be great if someone takes it up, else I'll add the docs to the book soon :).

[Evalir]

Closing as done & documented