Do not require &worker when executing {contract, account}.call

[ChaoticTempest]

Accounts and Contracts do not need to take in worker when performing calls, but would end up requiring type parameters in the current state of the API. Once Worker no longer takes a type parameter and is resolved with this issue #31, then we can just add a Worker pretty simply into these types.

[austinabell]

Accounts and Contracts do not need to take in worker when performing calls, but would end up requiring type parameters in the current state of the API. Once Worker no longer takes a type parameter and is resolved with this issue #31, then we can just add a Worker pretty simply into these types.

Well, regardless of choosing traits vs. no traits this can still be done, but would just be a breaking change to add the generic on accounts and contracts.

[ChaoticTempest]

closed with #181