Restrict the logic for trace detection in logs

[maxday]

What does this PR do?

• Modify the logic to better discriminate a Datadog trace in logs
• Add units tests around the modified function

Before : traces array was enough
After : traces array + first item of the array containing a 'trace_id' field

Now logs containing the trace keyword, which are NOT Datadog traces, are correctly logged.

Before:

After:

Motivation

Support ticket

Testing Guidelines

• Unit testing
• redeploy a forwarder in sandbox

Types of changes

• Bug fix
• New feature
• Breaking change
• 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
• This PR passes the integration tests (ask a Datadog member to run the tests)
• This PR passes the unit tests