Use new observability query API

What does this MR do and why?

Uses new Observability Query API. This feature is behind the observability_tracing feature flag and the feature is still Experimental. It has only been enabled for certain projects in the gitlab-org and gitlab-com namespaces.

Backend changes have landed in gitlab-org/opstrace/opstrace!2275 (merged) and have been promoted to production.

Closes gitlab-org/opstrace/opstrace#2322 (closed)

Screenshots or screen recordings

Shows rendered traces from new API:

How to set up and validate locally

Unfortunately running the whole stack is not trivial and not really straightforward to run locally, so I've just attached a demo of these changes. If you want to play around with the changes, I can prepare a VM and share a VPN config with you so you can connect to it and test it.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.