Replace ImportError with logging.warning if dpctl version is not met

[oleksandr-pavlyk]

If dpctl was built from source without .git folder present, dpctl.__version__ is 0+unknown and dpctl_version computation in numba_dpex/dpctl_support.py broke down.

Introduced function to safely infer dpctl_version, and modified config.py to issue soft logging.warning about unmet dpctl version instead of raising hard ImportError.

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[diptorupd]

Merge based on public CI.