Improvements to the Grafana LGTM dashboards

[brunobat]

Description

After PR #41264

There are some improvements that need to be performed:

• - Increment the the Grafana LGTM image version to the latest (v0.7.4 when this issue was created) because if supports configurable dashboards. (@brunobat)
• - Fix scraper port and prometheus.yaml file
• - Add dashboard for the Micrometer to OpenTelemetry bridge. (@brunobat )
• - After updating the image version add a grafana-dashboards.yaml at /otel-lgtm/grafana/conf/provisioning/dashboards and remove the hack in LgtmContainer.java. (@brunobat)
• - Explain in the documentation how to access the Quarkus dashboards
• - Fix some layout issues.
• - Increase the scraper frequency. (@alesj)
• - In devmode, Increase default output rate so data shows quicker on the dashboards. (@alesj)
• - Only activate the scraper if the Prometheus registry is present. (@alesj)
• - Having the max request is not very useful and I left them blanc... I would rather try to display percentils: 90%, 99% and 99.9%
• - The I/O overview is just a repetition on the HTTP panels. (@alesj )
• - We should probably display a total error count or rate with 4** and 5** requests. Check this on HTTP and see if this makes sense. (@alesj )

CC @melloware @gastaldi

Implementation ideas

No response

[brunobat]

In devmode export rates should be quicker:

• The quarkus.otel.metric.export.interval should be tweaked
• For spans: quarkus.otel.bsp.schedule.delay
• For logs: quarkus.otel.blrp.schedule.delay