Update threshold to use checks metrics instead of errors

[SandGrainOne]

Description

I've been using this time to learn more about k6 in preparation for issue #562 and this pull request is the result.

• Changing the threshold rule for all tests and removing the custom "error" metric.
• Simplified the stopInterationOnFail method and updated call points.

Related Issue(s)

• 562

Verification

• [x] Your code builds clean without any errors or warnings
• [x] Manual testing done (required)

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud