`pre-main-kyma-gardener-gcp-eventing-upgrade` is flaky

[friedrichwilken]

pre-main-kyma-gardener-gcp-eventing-upgrade is flaky and regularly fails with:

1) Eventing tests
       with Nats backend
         In-cluster event should have correct tracing spans:
     Error: cannot get jaeger trace
404: Not Found: {"data":null,"total":0,"limit":0,"offset":0,"errors":[{"code":404,"msg":"trace not found"}]}
      at convertAxiosError (utils/index.js:116:10)
      at getJaegerTrace (tracing/client.js:23:11)
      at processTicksAndRejections (internal/process/task_queues.js:95:5)
      at async checkTrace (test/fixtures/commerce-mock/index.js:323:20)
      at async checkInClusterEventTracing (test/fixtures/commerce-mock/index.js:319:3)
      at async Context.<anonymous> (eventing-test/eventing-test.js:200:7)

[nachtmaar]

Would be nice if the test would print out the URL which is giving the 404. Any other information which might have helped to debug this by solely looking at the logs are appreciated :)

[friedrichwilken]

we found that there is an issue with the lastorder function due to changes in kyma internals during the upgrade. This can be resolved by rebuilding the function after the upgrade.

[friedrichwilken]

This PR is going to resolve this issue: https://github.com/kyma-project/kyma/pull/15792

[friedrichwilken]

This PR will rise the test's reliability further: #15769