Scaffolding Tracing Details UI

What does this MR do and why?

Setup route (tracing/:id) and basic view for the Tracing Details UI.

Related FE changes: !127210 (merged)

Closes gitlab-org/opstrace/opstrace#2290 (closed)

(Note this is an Experimental feature. No real customers yet)

Screenshots or screen recordings

Nothing to see yet!

How to set up and validate locally

• Feature.enable(:observability_tracing)
• Go to https://local.gitlab.com:3443/flightjs/Flight/-/tracing/foo
• From the browser JS console, check that the div placeholder is set up correctly

document.getElementById('js-tracing-details')

<div data-view-model=​"{"tracingIndexUrl":​"/​flightjs/​Flight/​-/​tracing","traceId":​"foo","tracingUrl":​"https:​/​/​observe.gitlab.com/​query/​31/​6/​v1/​traces","provisioningUrl":​"https:​/​/​observe.gitlab.com","oauthUrl":​"https:​/​/​observe.gitlab.com/​v1/​auth/​start"}​" id=​"js-tracing-details">​</div>​

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.