dpctl should provide cmake config files and install them

[diptorupd]

The FindDpctl.cmake is not installed as part of the conda package nor do we currently provide a DpctlConfig.cmake file. The result is that dpctl cannot be found by external cmake projects.

CMake Error at CMakeLists.txt:7 (find_package):
By not providing "FindDpctl.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "Dpctl", but
CMake did not find one.

Could not find a package configuration file provided by "Dpctl" with any of
the following names:

DpctlConfig.cmake
dpctl-config.cmake

Add the installation prefix of "Dpctl" to CMAKE_PREFIX_PATH or set
"Dpctl_DIR" to a directory containing one of the above files. If "Dpctl"
provides a separate development package or SDK, be sure it has been
installed.

[oleksandr-pavlyk]

I think this would be closed by #853.

With #853 all one needs to do python setup.py develop -- -DPDCTL_MODULE_PATH=$(python -m dpctl --cmakedir) to build external package which uses dpctl via find_package(dpctl) in their CMakeLists.txt.

[oleksandr-pavlyk]

No, we should create dpctlConfig.cmake and make sure it installed in $PREFIX/share/cmake/dpctl/dpctlConfig.cmake.

Thus would allow find_package(Dpctl REQUIRED) to work without setting any additional module path variables.