Add a way for users to enumerate all possible arguments understood by `device_context`

[diptorupd]

Python 3.7.7 (default, Jul 14 2020, 22:02:37)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.17.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import dpctl

In [2]: with dpctl.device_context('level0:gpu:0'):
   ...:     print(dpctl.get_current_queue().get_sycl_device().dump_device_info())
   ...:
TBB Warning: The number of workers is currently limited to 11. The request for 31 workers is ignored. Further requests for more workers will be silently ignored until the limit changes.

    Name            Intel(R) Gen9
    Driver version  1.0.17767
    Vendor          Intel(R) Corporation
    Profile         FULL_PROFILE
    Device type     gpu
None

In [3]: with dpctl.device_context('level0:gpu:0'):
   ...:     dpctl.get_current_queue().get_sycl_device().dump_device_info()
   ...:
    Name            Intel(R) Gen9
    Driver version  1.0.17767
    Vendor          Intel(R) Corporation
    Profile         FULL_PROFILE
    Device type     gpu

In [4]: with dpctl.device_context('opencl:gpu:0'):
   ...:     dpctl.get_current_queue().get_sycl_device().dump_device_info()
   ...:
    Name            Intel(R) Gen9 HD Graphics NEO
    Driver version  20.35.17767
    Vendor          Intel(R) Corporation
    Profile         FULL_PROFILE
    Device type     gpu

In [5]:

Notice the TBB warning on the first invocation.

It would be nice if dpctl provided a function to enumerate all possible arguments understood by device_context, even if only to be used to construct an informative error message.

Originally posted by @oleksandr-pavlyk in #93 (comment)

[diptorupd]

device_context and Sycl* objects constructors that support filter selectors now properly implement sycl::ONEAPI::filter_selector and have same syntax.