What does this PR do?

Conditions ddtrace version based on runtime; Python 3.8 and 3.9 layers will use ddtrace versions >=3.19.1 and <4, while Python 3.10 and above will use ddtrace versions >=4 and <5.

Motivation

ddtrace released v4 a few weeks ago with breaking changes and many bug fixes; this PR aligns the lambda layer with that release.

Testing Guidelines

Additional Notes

Types of Changes

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

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• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
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