Fix cross-account/cross-regions SNS subscriptions to topics with the same name

[zvymazal]

What did you implement:

Closes #6444

How did you implement it:

If Lambda function subscribes to multiple topics with the same name allow defined topicName to take precedence when creating CloudFormation resources and to prevent resource name collisions.

How can we verify it:

Configure two topics with the same name in two different accounts (or in two different regions):

functions:
  hello:
    handler: handler.run
    events: 
      - sns: 
        arn: arn:aws:sns:us-east-1:00000000000:topicname
        topicName: topicname-account-1-us-east-1
      - sns: 
        arn: arn:aws:sns:us-east-1:11111111111:topicname
        topicName: topicname-account-2-us-east-1

Deployment should succeed without an error. Check if two CloudFormation resources of type AWS::SNS::Subscription exist and if they have "sanitized" name taken from topicName.

Todos:

Note: Run npm run test-ci to run all validation checks on proposed changes

• Write tests and confirm existing functionality is not broken.
  Validate via npm test
• Write documentation
• Ensure there are no lint errors.
  Validate via npm run lint-updated
  Note: Some reported issues can be automatically fixed by running npm run lint:fix
• Ensure introduced changes match Prettier formatting.
  Validate via npm run prettier-check-updated
  Note: All reported issues can be automatically fixed by running npm run prettify-updated
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[pmuens]

Thanks for working on this @zvymazal 👍

Could you add a regression test case so that we can be sure to not re-introduce that bug in the future? Thanks!

[pmuens]

Thanks for working on this @zvymazal 👍

I just tested it and this PR fixes the bug. LGTM