Rename dpctl capi

[diptorupd]

The name dpctl-capi is misleading and a legacy of a previous design vision for dpctl. The PR renames dpctl-capi to libsyclinterface to better reflect the intent of the helper library, i.e., to provide a C API wrapper for DPC++'s SYCL run time.

[coveralls]

Coverage remained the same at 74.445% when pulling d453e7d on diptorupd:rename-dpctl-capi into f292953 on IntelPython:master.

[oleksandr-pavlyk]

Should we then also restructure dpctl_installation_dir/include to the following layout?

  include/
    sycl_interface/
        Config/
        Support/
        *.h   /* all *.h files from present include/*.h */
    dpctl/
         dpctl_api.h    /* shallow files containing #include "../../_sycl_queue_api.h" and others */
    pybind11/
         dpctl.h        /* definitions for the C++ classes and casters to/from dpctl Python types */

[diptorupd]

Should we then also restructure dpctl_installation_dir/include to the following layout?

  include/
    sycl_interface/
        Config/
        Support/
        *.h   /* all *.h files from present include/*.h */
    dpctl/
         dpctl_api.h    /* shallow files containing #include "../../_sycl_queue_api.h" and others */
    pybind11/
         dpctl.h        /* definitions for the C++ classes and casters to/from dpctl Python types */

Let us do these changes in a follow up PR.

[AndresGuzman-Ballen]

This PR has the devil's mark :O