[FEA]: Automate documentation for libcu++ Standard Library header support

### 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

libcu++

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

As a user of libcu++, I want to know what Standard Library headers and features are supported.

However, keeping a list manually updated of what headers/features we support is a recipe for stale documentation.

### Describe the solution you'd like

I'd like an automated solution that can parse the headers in libcu++ and generate a table of what Standard Library headers we support (alongside any limitations or caveats).

One thing to consider is we could also parse our feature test macro definitions and build a table of which features we support based on that.

See:
- https://en.cppreference.com/w/cpp/utility/feature_test
- https://github.com/NVIDIA/cccl/blob/main/libcudacxx/include/cuda/std/detail/libcxx/include/version

### Describe alternatives you've considered

_No response_

### Additional context

_No response_