Implement a helper alias template for complex types

[antonwolfy]

The PR proposes to implement own alias template is_complex rather than relying on internal one from SYCL library, since it is from internal SYCL namespace, also it might have a limitation (for instance, latest DPC++ package for 2024.1 breaks dpnp compilation on Windows) and not indented initially to be used in host code.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/index.html

[vtavana]

Thank you, @antonwolfy!