Use HDK class in examples + some new examples

[akroviakov]

This PR introduces the following example usages:

• Change basic_python_usage.ipynb to use HDK class (now used in all examples).
• Taxi example simplified due to HDK class usage.
• Manually construct query graphs.
• • Showcase the benefit of compilation.
• • Show how one can run a query graph on CPU/GPU/some part on CPU and some part on GPU.
• Allow relatively easy table generation for heterogeneous aggregation performance analysis (with plots).

Some minor updates in HDK class in hdk.py: allow table refragmenting and easy gpu memory cleanup.

[kurapov-peter]

Looks good. Please check the debug_logs usage.

[akroviakov]

Modin doesn't use debug_logs:

~/modin$ grep -r "debug_logs"
~/modin$