fix: Modify ASM logic to honor addExtension as well as enableASM config

[astuyve]

What does this PR do?

The enableASM functionality had two faulty logic components:

1. It never checked the value of enableASM, only the presence. So enableASM: false would still attempt to enable ASM.
2. It never checked the presence of the Datadog Extension. The Extension provides the binary used by AWS_LAMBDA_WRAPPER and without it, the function crashes.

Motivation

Fixes #480

Testing Guidelines

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)
• [x] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 76.33%. Comparing base (5b4bc42) to head (a2f7805).

:exclamation: Current head a2f7805 differs from pull request most recent head 9cd4a32. Consider uploading reports for the commit 9cd4a32 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #481 +/- ## ======================================= Coverage 76.33% 76.33% ======================================= Files 12 12 Lines 955 955 Branches 299 299 ======================================= Hits 729 729 Misses 164 164 Partials 62 62 ```

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[Fodoj]

Does it also fix https://github.com/DataDog/serverless-plugin-datadog/issues/477 ?