Review tracing support

[DrPsychick]

Motivation:

Tracing may help to find issues and report bugs. Current support in the Chart seems unfinished or untested. Also, the Chart seems to not support tracing with an external installation.

• Test with jaeger.enabled: true and set the jaeger.url from the deployment
• Add tracing.enabled: true to allow use of an external tracing deployment (https://www.jaegertracing.io/docs/1.60/operator/#quick-start---deploying-the-allinone-image, https://grafana.com/oss/tempo/, https://zipkin.io/)