chore(rds): support more AWS RDS DB Instance engines in encryption check

[madereddy]

Context

Add additional RDS transport level encryption logic for supported RDS versions:

For SQL Server, PostgreSQL and Aurora PostgreSQL databases, if the rds.force_ssl parameter value is set to 0, the Transport Encryption feature is not enabled. For MySQL, Aurora MySQL and MariaDB databases, if the require_secure_transport parameter value is set to OFF, the Transport Encryption feature is not enabled.

Description

Added additional checks for MySQL, MariaDB, Aurora PostgreSQL, and Aurora MySQL DB instances.

Corrected Microsoft SQL Server checks as well to include all the engine versions available.

License

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

[madereddy]

Taking place over #3964 to keep a clean commit.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.52%. Comparing base (ebe3c5d) to head (e210238).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3968      +/-   ##
==========================================
+ Coverage   86.44%   86.52%   +0.07%     
==========================================
  Files         768      768              
  Lines       23884    23889       +5     
==========================================
+ Hits        20646    20669      +23     
+ Misses       3238     3220      -18     

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