Add support for raw_kernel_arg extension

[sommerlukas]

Add support for the DPC++ SYCL extension raw_kernel_arg that allows to pass a binary blob as kernel arguments.

This is for example useful if the kernel uses a struct as kernel parameter, but is loaded from SPIR-V and the argument type is unknown for set_arg.

The implementation follows #1984.

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• Have you made sure that new changes do not introduce compiler warnings?
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[coveralls]

coverage: 86.321% (-0.06%) from 86.379%
when pulling 1ea6b9c on sommerlukas:raw-kernel-arg
into 67317b0 on IntelPython:master.

[AlexanderKalistratov]

auto RawArg = unwrap<RawKernelArgData>(Ref);
delete[] RawArg->bytes;
delete RawArg;

[AlexanderKalistratov]

Sorry. I've misled you in my previous comment about unique_ptr. To make it work it should be something like this:

        auto rawData =
            std::unique_ptr<unsigned char[]>(new unsigned char[count]);
        std::memcpy(rawData.get(), bytes, count);
        auto RawKernelArg = std::unique_ptr<RawKernelArgData>(
            new RawKernelArgData{rawData.get(), count});
        rka = wrap<RawKernelArgData>(RawKernelArg.get());
        RawKernelArg.release();
        rawData.release();

Otherwise rawData would leak if new RawKernelArgData{rawData.release(), count} throws.

[ndgrigorian]

@sommerlukas
Master now has a fix for nightly build, so please merge or rebase on master so the tests run on nightly compiler