Rename PyDPPL to dpCtl

[diptorupd]

pyDPPL is to be renamed to dpCtl and the Python module is to be renamed to dpctl.

It is necessary to make it safer:

1. add new API
2. reimplement the old API via new API
3. mark old API as deprecated
4. remove old API in the next release

Related to #123.

[PokhodenkoSA]

Todo for dpCtl:

• Rename module dppl to dpctl (Rename module from dppl to dpctl #48)
• Rename package from pydppl to dpctl (Rename package PyDPPL to dpCtl #49)
• Rename GitHub repo from IntelPython/pydppl to IntelPython/dpCtl
• Update CI for new package name
• Rename file and folder names from dppl* to dpctl*
• Rename env variables like DPPL_SYCL_INTERFACE_LIBDIR
• rename backends to dpctl-capi

Todo for Numba:

• Rename usage cases in https://github.com/IntelPython/numba from dppl to dpctl (Rename PyDPPL/dppl to dpCtl/dpctl numba#49)
• Change dependency of https://github.com/IntelPython/numba to package from pydppl to dpctl
• Rename submodule in https://github.com/IntelPython/numba from dppl to dppy
• Rename the main branch in https://github.com/IntelPython/numba from pydppl to dppy
• Rename dppl to dppy numba-dpex#8 Rename dppl to dppy in numba-dppy

[diptorupd]

@PokhodenkoSA Can we get this in for 0.5.0? We need to let downstream projects like daal4py and dpnp be aware of these changes.

[PokhodenkoSA]

Can we get this in for 0.5.0?

Yes. @1e-to does the work for renaming in numba-dppy - IntelPython/numba-dpex#42

[diptorupd]

All dpctl changes are complete (#201). The Numba-dppy changes are being tracked in numba-dppy PR#42. I will close the issue once the numba-dppy PR is merged.

[diptorupd]

All changes have been completed.