Report unhealthy containers as part of the jUnit test failures

[mrodm]

Sometimes running system tests could fail because the service used for testing cannot be started or is unhealhty.

Example of this could be checked in this build:
https://buildkite.com/elastic/integrations/builds/14993#0191872e-6ce6-42fe-bea3-a48376ff96d8

Service was unhealthy after the default timeout and that was reported by elastic-package:
Error: error running package system tests: could not complete test run: could not setup service: service is unhealthy: timeout waiting for healthy container

The issue is that this error is not part of the test failures reported in the XML (jUnit). It would be better to add this kind of errors as another error in the corresponding test case.

Something to remark here, is that even if these errors are added into the test files, not sure if the test run could continue. Currently, this kind of errors makes fail the whole execution of tests.