Update opencl interoprability code to fix build with open source llvm/sycl bundle

[oleksandr-pavlyk]

Closes #624

Replaced sycl::context::get() with
sycl::context::get_native<sycl::backend::opencl>().

[coveralls]

Coverage remained the same at 74.419% when pulling 67afcec on fix-opencl-interop into da90ebd on master.

[diptorupd]

Is the internal CI failures due to DPC++ version incompatibility?

[oleksandr-pavlyk]

Is the internal CI failures due to DPC++ version incompatibility?

Seems to be an internal infra script problem:

  Traceback (most recent call last):
09:40:09
  Test deps                = ['pytest-cov', 'cython', 'pytest', 'teamcity-messages']
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    File "teamcity-integration/src/pypi/testing.py", line 81, in <module>
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  Path to smoke tests      = None
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      add_library_path=apply_workaround)
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  Path to functional tests = /localdisk/tools/tc/agent1/work/4f533563c9f3b284/dpctl/run_test.sh
09:40:09
    File "/localdisk/tools/tc/agent1/work/4f533563c9f3b284/teamcity-integration/src/pypi/tools.py", line 160, in setup_pypi_environment
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  Setup pypi_test venv environment for python 3.8
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      raise Exception('\n'.join(output))
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  conda remove -q -y --name pypi_test --all
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  conda create -q -y -n pypi_test python=3.8 pip -c anaconda --override-channels
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  Exception: source /localdisk/tools/tc/agent1/work/4f533563c9f3b284/base/etc/profile.d/conda.sh && conda activate pypi_test && python -m venv /localdisk/tools/tc/agent1/work/4f533563c9f3b284/pypi_test_venv --clear
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  -------------------------------------------------------------------------------
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  /bin/sh: 1: source: not found
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  source /localdisk/tools/tc/agent1/work/4f533563c9f3b284/base/etc/profile.d/conda.sh && conda activate pypi_test && python -m venv /localdisk/tools/tc/agent1/work/4f533563c9f3b284/pypi_test_venv --clear
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  -   -   -   -   -   -   -   -   -   -   -   -   -   -   -   -   -   -   -   -
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  /bin/sh: 1: source: not found
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  Process exited with code 1
09:40:09
  Process exited with code 1 (Step: testing with local perflibs (Command Line))