Dpctl

Added
- Device descriptors "max_compute_units", "max_work_item_dimensions", "max_work_item_sizes", "max_work_group_size", "max_num_sub_groups" and "aspects" for int64 atomics inside dpctl C API and inside the dpctl.SyclDevice class.
- MemoryUSM* classes moved to `dpctl.memory` module, added support for aligned allocation, added support for `prefetch` and `mem_advise` (sychronous) methods, implemented `copy_to_host`, `copy_from_host` and `copy_from_device` methods, pickling support, and zero-copy interoperability with Python objects which implement `__sycl_usm_array_inerface__` protocol.
- Helper scripts to generate API documentation for both C API and Python.

Fixed
- Compiler warnings when building libDPPLSyclInterface and the Cython extensions.

Removed
- The Legacy OpenCL interface.

Changed
- How the initial active queue is populated inside DPPLQueueMgr.
- dpctl.SyclQueueManager only reports the number of non-host platform.
- dpctl.SyclQueueManager now raises an exception if DPCTL C API returns a nullptr instead of a valid Sycl queue.

Fixed
- Several crashes in cases where an OpenCL or Level Zero platform is not available.
- Fix failing platform test case. [116](https://github.com/IntelPython/dpctl/pull/116)
- Properly skip tests when no OpenCL devices are available.
- Add skip tests to test_sycl_usm.py
- Fix Gtests configuration.

Fixed
- A crash on Windows due a Level Zero driver problem. Each device was getting enumerated twice. To handle the issue, we added a temporary fix to use only first device for each device type and backend [118](https://github.com/IntelPython/dpctl/pull/118).

Added
- Changelog was added for dpctl.

Fixed
- Windows build was fixed.

Added
- Add a helper function to all Python SyclXXX classes to get the address of the base C API pointer as a long.

Changed
- Rename PyDPPL to dpCtl in comments (function name renaming to come later)

Fixed
- Fix bugs highlighted by tools.
- Various code clean ups.

Added
- Dump functions were enhanced to print back-end information.
- dpctl gained support for unint_8 and unsigned long data types.
- oneAPI Beta 10 tool chain support was added.

Changed
- dpctl is now aware of DPC++ Sycl PI back-ends. The functionality is now exposed via the context interface.
- C API's queue manager was refactored to require back-end.
- dpct's device_context now requires back-end, device-type, and device-id to be provided in a string format, e.g. opencl:gpu:0.

Fixed
- Fixed some important bugs found by static analysis.