Feature Request: <Transaction /> should accept an async function in calls prop

### Describe the solution you'd like

I would like the component to accept an async function in the calls prop that resolves to calls.

I would much rather have a component that looks like this:
```typescript
await fetchCalls() as Call[]}
chainId={{base.id}}
>
Buy

```

Rather than setup a component such that I need to find a creative way for my calls to be constantly updating in a useMemo or something like that.

### Describe alternatives you've considered.

Instead of having my calls prop behave like a promise where I can fetch calls and then return the calls to the transaction button, I need to do extra work to ensure that my calls are memoized and stay updated based on user behavior.

Example: consider the situation where a user controls an input field and based on the amount that they enter, I need to fetch a quote and create calls based on the quote. In the current setup, I need to watch the input field and fire off a query to fetch a quote when the input changes.

If instead I could pass an async function to the transaction component, I could execute the fetch for the quote only once and then return the calls to the transaction component at the time of execution.