Request Timeouts dynamically calculated

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

I am trying to set the timeout of my request dynamically, but it seems it must be a constant value.

### Describe the solution you'd like

I would suggest that `UseRequestTimeouts` have a callback option with the request context to be evaluated and set the timeout value inside of this callback.

### Additional context

I am using .net in Lambda, and I could use `ILambdaContext.RemainingTime - buffer` to determine when the timeout should happen, but I don't see how to do so with the current implementation.