fix: Wrap logError in conditional for isAgentRunning, as this is now the agent's responsibility

[astuyve]

What does this PR do?

Use logDebug instead of logError if the Agent (extension) is running. The API key is required there, not by this library (unless we are using the forwarder and sending metrics to the backend from this library)

Motivation

Fixes DataDog/serverless-plugin-datadog#237

Testing Guidelines

Additional Notes

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)

[codecov-commenter]

Codecov Report

Merging #273 (42f89c3) into main (300ef85) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main     #273   +/-   ##
=======================================
  Coverage   82.69%   82.69%           
=======================================
  Files          37       37           
  Lines        1630     1630           
  Branches      354      354           
=======================================
  Hits         1348     1348           
  Misses        234      234           
  Partials       48       48           

Impacted Files	Coverage Δ
src/metrics/listener.ts	87.65% <0.00%> (ø)

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[hghotra]

👍🏼