Removed use of dpcpp_kernels.hpp

Straightforward attempt to transition from using deprecated sycl::program
to kernel_bundle caused crashes. SYCL spec stipulates that cgh.parallel_for(.., kernel)
is intended for interoperability kernels only, and dpcpp_kernels.hpp was creating
non-interoperability kernel objects.

The intent of dpcpp_kernels was improve test coverage of syclinterface, but this
was addressed by also collecting library coverage info when running pytests

Author: oleksandr-pavlyk