[OFFLOAD] Recognize level_zero backend in liboffload (#172818)
The code to recognize the level_zero plugin as a liboffload backend was
split from #158900. This PR adds the support back.
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Co-authored-by: Alexey Sachkov <alexey.sachkov@intel.com>
Co-authored-by: Nick Sarnie <nick.sarnie@intel.com>
Co-authored-by: Joseph Huber <huberjn@outlook.com>