Add Tracing List UI

What does this MR do and why?

• Add Tracing's Getting Started page (gitlab-org/opstrace/opstrace#2267 (closed))
• Add Tracing List UI (gitlab-org/opstrace/opstrace#2249 (closed))
• Adding spinner variant to skeleton + fixed animation ( had to make a backcompatible fix as otherwise some e2e tests started failing. Decided not to fix the tests as those tests are going to be removed soon )

Closes gitlab-org/opstrace/opstrace#2249 (closed), gitlab-org/opstrace/opstrace#2267 (closed)

Screenshots or screen recordings

How to set up and validate locally

• Enable FeatureFlag :observability_tracing
• Comment this this out:

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.