[sls-951] Add DEBUG logs to datadog-cloudformation-macro

[hghotra]

What does this PR do?

https://datadoghq.atlassian.net/jira/software/projects/SLS/boards/205

Motivation

When customers have issues using the datadog-cloudformation-macro, it would be helpful to have CloudWatch logs from the macro Lambda function in order to debug their issues.

Testing Guidelines

Deploy a sample application which uses the datadog-cloudformation-macro

Additional Notes

Types of changes

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [x] Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• [ ] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [ ] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog