[DISCUSSION] Add `DedicatedExecutor` into the DataFusion crates to make using multiple threadpools easier

[alamb]

Is your feature request related to a problem or challenge?

• Related to Document DataFusion Threading / tokio runtimes (how to separate IO and CPU bound work) #12393

Describe the solution you'd like

As explained on the following PR:

• Example for using a separate threadpool for CPU bound work (try 2) #14286

I implemented a version of DedicatedExecutor and an example showing how to use multiple thread pools with DataFusion. However, the example is currently very large as it uses an abstraction called DedicatedExecutor to manage sending work back and forth between the runtimes

If users want to do the same thing, they will need to copy DedicatedExecutor into their code (or make something similar).

Describe alternatives you've considered

If DedicatedExecutor is a useful API for multiple people I think we should consider moving it into one of the core crates

Additional context

No response