feat(`cheatcodes`): add `vm.expectTransfer`

Currently there are multiple flavors of `expectCall`, but all of them treat empty `data` as a request to not check the calldata content. The problem is that there's no way to check if calldata is empty, e.g. because a native token transfer was made. The current `expectCall` API surface doesn't leave much space for adding this feature.

I propose adding a new set of `expectTransfer` functions. They would be identical to `expectCall` with all their variants, but they wouldn't have the `data` parameter, and they would expect that the address is called with zero-length calldata.