Improvements to dpctl documentation website

[diptorupd]

Several aspects of dpctl documentation need to be improved. This ticket collects everything that needs to be cleaned up.

• [ ] Missing user guides
  • [x] Device selection
  • [ ] Event profiling
  • [ ] Queue profiling
  • [ ] Creating different types of queues
  • [x] Sub-devices
• [x] Add examples to Python API functions and add them to docstrings
• [x] Fix and improve C API docstrings
• [ ] Improve the overview
• [x] Missing Python docstrings
• [x] Inconsistent styling between C API and Python API
• [x] Broken links in C API
• [x] Missing examples in Python API
• [ ] Missing programming guide for C API (mention PIMPL, pointer ownership macros, organization of modules, etc.)
• [ ] Fix support for multi-version links in the sidebar. Currently we are using an hard coded value to our github.io site. Can we use a cleaner solution e.g. using sphinx-multiversion?
• [ ] Copyright year should not be hard-coded.

[diptorupd]

@oleksandr-pavlyk @ndgrigorian I will let you judge if any of these suggestions make sense with your overall vision of improved dpctl documentation pages. Feel free to close the issue if you feel it is redundant at this point of time.