Add sycl::ext::oneapi::experimental::printf to the supported extensions list

The `sycl::ext::oneapi::experimental::printf` is currently experimental extension heavily used in the projects with SYCL kernels such as Pytorch for debug.

* Documentation for this extension seems missing in https://github.com/intel/llvm/tree/sycl/sycl/doc. Can it be added?
* Can this extension be promoted from experimental to supported?

See: https://github.com/intel/torch-xpu-ops/blob/9022a83389905509033d02cda8005c21be9c976c/src/comm/SYCLHelpers.h#L347

CC: @gmlueck, @EikanWang, @guangyey

Start by reviewing the SYCL documentation directory at sycl/doc and the printf usage in SYCLHelpers.h around line 347. Determine the documentation needed and the requirements for moving sycl::ext::oneapi::experimental::printf into the supported extensions list. Done means the extension is documented and its support status is updated, subject to maintainer agreement.

Written by the indexing model from the issue text.