Allow specifying RequestStrategy on per request on next

[TroyKomodo]

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

Currently the config override is specified on a per request basis but there is no way for any client to modify this value.

The difference between doing this and constructing a new client is this will reuse the underlying hyper connection pool. If we invoke the client builder (the only way i found to set the request strategy) we create an entirely new connection pool.

Describe the solution you'd like

Ideally I would like

These 2 methods to be exposed on the CustomizedStripeRequest struct aswell so we can do something like this

Describe alternatives you've considered

Currently we are resorting to this.

Additional context

No response

[mzeitlin11]

Thanks for trying out the next branch and suggesting improvements @TroyKomodo! The current structure and approach toward allowing custom clients is pretty early stages, so any ideas to improve ergonomics like this one are very welcome. I hope to have more time to work on changes like this soon, but also happy to review any contributions!