Use [[deprecated("msg")]] annotation only for C++ builds

[oleksandr-pavlyk]

Changed libsyclinterface/include/dpctl_sycl_device_interface.h to only use [[deprecated("msg")]] annotation for C++ builds.

This fixes build of numba-dpex's native extension. This remained broken despite claim to the contrary in #879.

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@mingjie-intel

[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/897/index.html

[coveralls]

Coverage remained the same at 81.842% when pulling cbaef17 on use-deprecated-only-for-cpp into 8655e98 on master.

[diptorupd]

LGTM! Please merge.

[oleksandr-pavlyk]

Actually, perhaps the check can be relaxed somewhat. The C extension added in #879 builds fine with gcc 11.2 packaged in conda c compiler package, while It was failing for me locally with gcc 9.4 installed on Ubuntu 20.04.

[oleksandr-pavlyk]

[[deprecated]] is part of C23 standard. It is supported in GCC, see https://en.cppreference.com/w/c/23

This explains why it breaks for me on GCC 9.4, but works with Anaconda's compiler which is GCC 11.2

[github-actions]

Deleted rendered PR docs from intelpython.github.com/dpctl, latest should be updated shortly. 🤞