Ensure NGINX reload occurs

[ciarams87]

Proposed changes

Problem:
When we reload NGINX, we do not check whether the reload succeeds. We just sleep for a second to wait for the new workers to spin up. We need to verify that a reload was successful and return an error if it fails.

Solution: First check if NGINX accepted the reload by confirming using the /proc filesystem that new workers are being created. Then use a configVersion check to ensure the expected version of the configuration is being served by the workers to confirm the reload was successful.

Testing: Manual testing with successful config and incorrect config, added and updated unit-tests, ensured conformance tests still pass

Closes #664

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[kate-osborn]

🚀