Revert "Remove py36 references"

[ewanek1]

Begins to resolveIssue 603. This PR removes all explicit references and workarounds for Python 3.6 across the codebase and documentation to support minimum Python version 3.7+.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.96%. Comparing base (347cb5e) to head (e444ff9).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@ Coverage Diff @@## main #1331 +/- ##
=======================================
Coverage 90.96% 90.96% =======================================
Files 222 222 Lines 7501 7501 =======================================
Hits 6823 6823 Misses 678 678 

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