[DF] Port Nested Subqueries to Datafusion

[jdye64]

Is your feature request related to a problem? Please describe.
Nested subqueries need to be ported from the Apache Calcite data structures to the Apache Datafusion data structures.

Describe the solution you'd like
All references should be removed from select.py, and likewise any other locations where subqueries could be present. All instances of calcite references removed should be replaced with the correlating Apache Datafusion data structures.

Success criteria for this port being complete is all pytests passing for test_select.py

Describe alternatives you've considered
None

Additional context
None

[andygrove]

This depends on apache/datafusion#2219

[jdye64]

Closed with PR #581