Add dpctl.SyclQueue.memset() method

[vlad-perevezentsev]

This PR proposes adding dpctl.SyclQueue.memset and dpctl.SyclQueue.memset_async methods as a Python wrapper over sycl::queue::memset backed by the existing DPCTLQueue_Memset and a new DPCTLQueue_MemsetWithEvents C-API function and adding a new test_sycl_queue_memset.py

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[github-actions]

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

[vlad-perevezentsev]

@ndgrigorian I implemented cpdef memset without validating val, i.e. matching sycl::queue::memset semantics where the value is silently truncated toits least significant byte.
Does it make sense to explicitly validate that val is within [0, 255]?

[coveralls]

Coverage is 74.51% — add_sycl_queue_memset into master. No base build found for master.

[ndgrigorian]

LGTM, thank you @vlad-perevezentsev