[EPIC] Design user-defined tuning API for cuda.parallel algorithms

### Is this a duplicate?

- [x] I confirmed there appear to be no [duplicate issues](https://github.com/NVIDIA/cccl/issues) for this request and that I agree to the [Code of Conduct](CODE_OF_CONDUCT.md)

### Area

cuda.cccl.parallel (Python)

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

As a user of `cuda.cccl.parallel` algorithms, I'd like to have a way to specify user-based tuning policies (e.g., items per thread, threads per block). This is similar to https://github.com/NVIDIA/cccl/issues/1186 for enabling the same thing in CUB C++ APIs. This issue describes designing a functionally similar interface for passing tunings in Python.

### Describe the solution you'd like

Something that parameterizes algorithms with an optional "environment" that allows me to control tuning parameters (and other things? memory resources?).

### Describe alternatives you've considered

_No response_

### Additional context

_No response_