Node.js agent v5.13.1

Improvements

Added diagnostic code injector.
The agent may now be configured to make transaction state checks via code injection. This may be turned on by setting code_injector.diagnostics.enabled to true. While this option is enabled, code around async boundaries will be added to track transactions, and log a message when they are not properly reinstated.
Added back generation of entity stats logging and uninstrumented support metric generation on metric harvests.
Removed legacy harvest code from main agent.
Upgraded tap to latest version
Upgraded mocha to latest version.
Adds --exit flag to mocha test runs to prevent infinite runs on CI.

primary_application_id now defaults to 'Unknown' in serverless mode to allow Distributed Tracing to function correctly when NEW_RELIC_PRIMARY_APPLICATION_ID is not defined.
Updated https-proxy-agent to v3 for security fix.
Shoutout to @asturur for the contribution.
Fixed bug where API.shutdown() would not properly harvest when configured to.
Fixed bug where multiple agent restarts would cause the number of 'stopped' listeners to exceed limit.
Fixed inconsistent async return from collector API.
This could result in an infinite loop due to attempting to merge before clearing. This bug should not have impacted normal agent runs but was uncovered for certain test cases.
Fixed tests that leave work scheduled on the event loop.
Fixed issue that could result in vendor utilization detection failure. As a part of this fix, the request that hits the timeout will immediately abort instead of hanging around for the default timeout.