Revert Tag Formatting to JSON Object Arrays

[lizapressman]

What does this PR do?

In a previous PR to add DD_XXX env vars and tagging, I modified the tag formatting to be { [key: string]: string }; instead of { Key: string; Value: string }[]; but cloudformation requires the JSON object array for Tags so this PR reverts that change.

Motivation

Problem was reported here

Testing Guidelines

Updated all unit tests to what we now expect and everything seems to be passing and looking good

Additional Notes

Types of changes

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

Check all that apply

• [x] 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