Py27dict deepcopy performance

[marekaiv]

Issue #, if available: n/a

Description of changes:
Implement __deepcopy__ for Py27Dict and related classes in order to improve performance. The generic deep copy in copy works, but is slow.

Description of how you validated changes:
Unit tests were added, and existing unit tests cover Py27Dict functionality. We also timed how long the transform took for a large template before and after the changes (for a very large template, these changes reduced processing time by ~80%). We confirmed that the transformed templates were the same before and after the changes.

Checklist:

• Add/update unit tests using:
  • Correct values
  • Bad/wrong values (None, empty, wrong type, length, etc.) n/a
  • Intrinsic Functions n/a
• Add/update integration tests n/a
• make pr passes
• Update documentation not necessary
• Verify transformed template deploys and application functions as expected -- confirmed transformed template didn't change

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Merging #2331 (858a2e5) into develop (e7a1496) will increase coverage by 0.73%.
The diff coverage is 98.20%.

@@             Coverage Diff             @@
##           develop    #2331      +/-   ##
===========================================
+ Coverage    93.58%   94.31%   +0.73%     
===========================================
  Files           90       97       +7     
  Lines         6124     7089     +965     
  Branches      1260     1460     +200     
===========================================
+ Hits          5731     6686     +955     
- Misses         183      194      +11     
+ Partials       210      209       -1     

Impacted Files	Coverage Δ
samtranslator/model/api/api_generator.py	94.38% <92.95%> (+0.02%)	⬆️
samtranslator/__init__.py	100.00% <100.00%> (ø)
samtranslator/feature_toggle/dialup.py	100.00% <100.00%> (ø)
samtranslator/feature_toggle/feature_toggle.py	100.00% <100.00%> (+12.16%)	⬆️
samtranslator/intrinsics/actions.py	98.78% <100.00%> (+0.06%)	⬆️
samtranslator/intrinsics/resource_refs.py	95.83% <100.00%> (-0.17%)	⬇️
samtranslator/metrics/method_decorator.py	100.00% <100.00%> (ø)
samtranslator/metrics/metrics.py	100.00% <100.00%> (ø)
samtranslator/model/__init__.py	97.63% <100.00%> (-0.02%)	⬇️
samtranslator/region_configuration.py	77.77% <0.00%> (-22.23%)	⬇️
... and 41 more

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[CoshUS]

LGTM! Thanks for the PR!

[hawflau]

LGTM!