[DOC]: Provide more obvious documentation about what Standard Library headers CCCL supports

### Is this a duplicate?

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

### Is this for new documentation, or an update to existing docs?

Update

### Describe the incorrect/future/missing documentation

As a user of CCCL, I want to be able to quickly and easily reference which Standard Library headers are supported, in addition to any restrictions or extensions to that header. This is likely to be the most common use case for visiting libcu++ docs, so it should be as streamlined and convenient as possible.

If you know where to look, this information is available under the Standard API section, but this isn't as obvious or intuitive as it could be. Typical C++ users are familiar with thinking in terms of individual headers like `` and not more abstract groups like "Numerics Library" that contains multiple headers.

## Desired Solution

To make it easier to find and quickly parse what headers are available, I would like to add a section to the top of the ["Standard API"](https://nvidia.github.io/cccl/libcudacxx/standard_api.html) landing page that provides a table of every supported header, what version it was added, and whether there are any restrictions.

Effectively, this should be a concatenation of the tables that already exist in the various "Library" sub-pages, e.g.,

The main [libcu++ landing page ](https://nvidia.github.io/cccl/libcudacxx/index.html) should also be updated with a very obvious link to this page.

### If this is a correction, please provide a link to the incorrect documentation. If this is a new documentation request, please link to where you have looked.

_No response_

Start with the Standard API landing page and the existing Library sub-pages linked from it, comparing their header tables and current restrictions. Update the Standard API page with a consolidated supported-header table, then add an obvious link from the main libcu++ landing page; done means users can find each supported header, its added version, and restrictions quickly.

Written by the indexing model from the issue text.