Create guide that shows how to link traces between different KeptnApp deployments

[mowies]

Goal

As a user, I want to easily understand the concept of passing trace context down to several deployments that happen at different points in time. This will enable me to nicely visualize staged deployments and have their traces be linked together.

Details

• create a new guide under the Guides sections in the docs (docs-new/docs/guides)
• the guide should explain how to use the new spec.traceLinks field to the user's advantage with usage examples
• add images where possible (especially grafana dashboards)
• The following steps should be explained in the guide:

1. Deploy an application (e.g. podtato head) in a namespace (e.g. dev)
2. Explain how to inspect the trace of the related KeptnApp, using the traces in the Grafana dashboard
3. Retrieve a traceParent from the trace to add it as a link to another deployment of the sample application in a different namespace (e.g. production) by adding the traceParent to the spec.traceLinks in the other application.
4. Showcase how extra metadata can be attached to the trace to pass along
5. Let the other application deploy and show how the traces of the new application are linked together, to see that the deployment of the application in the dev namespace caused the deployment in production at a later point in time

[odubajDT]

A lot of information is already present in this PR #2880

Maybe it would be enough to have a short introduction about the feature and then link the guide

[mowies]

The team agreed to move the content in the observability getting started guide from #2880 to a new guide page that is done in this ticket. We decided to do that, because the context feature not immediately important to new users so the reason for it to exist in the getting started guide is not really warranted. But of course we still need a comprehensive guide that explains and presents the new context feature.