Make 'app-full-microprofile' project closer to what customers do and address engineering team feedback

[michalvavrik]

Changes based on https://issues.redhat.com/browse/QUARKUS-4073, however I must stress this is my opinionated interpretation of the feedback as sometimes the feedback wasn't detailed suggestion:

• use OpenTelemetry and make sure that Vert.x gRPC OTLP traces exporter is used (not using Jaeger container as we test Startstops without Linux containers)
• use Micrometer Prometheus registry instead of deprecated MP Metrics
• test serialization response as that is what most apps do rather than non-Quarkus code like building JWT tokens
• whether app is ready is more likely to be detected by probes than by requesting static content from index page, therefore the first request is measured by probes endpoint

[rsvoboda]

+1 for the changes, just two small items for adjustment.

Assuming you will backport these changes to 3.8 branch to make 3.8 and 3.14 results comparable.

[rsvoboda]

Thanks @michalvavrik!

Please prepare the same change for 3.8 branch. We will need new baseline comparison for 3.8 and main.