fix: add deletion policy to KMS keys

[carvantes]

Description of changes:

Add deletion policy policy to KMS keys. Without this the deletion policy on DDB and S3 buckets was not effective since the KMS key would be deleted an customers would lose access to S3/DDB data even if the Bucket/Table was retained

Checklist:

• Have you successfully deployed to an AWS account with your changes?
• Have you written new tests for your core changes, as applicable?

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 #540 (f2993e7) into develop (2604e59) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #540   +/-   ##
========================================
  Coverage    94.84%   94.84%           
========================================
  Files            1        1           
  Lines           97       97           
  Branches        14       14           
========================================
  Hits            92       92           
  Misses           5        5           

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