Follow-up "Move Tracing to Core"

This issue contains ideas for refactorings which came up while moving Tracing from GitLab Ultimate to GitLab Core.

Ideas

• !44604 (diffs) - Move Tracing route to scoped /-/tracing
• Namespace ProjectTracingSetting under Tracing::ProjectTracingSetting or Tracing::ProjectSetting -
• Move Project#tracing_external_url to a presenter - !43869 (comment 422066949)
• Check permission in the tracing operations service and other operations additionally to the check in the controller - !44303 (diffs, comment 423791300)
• Consider using let_it_be and before_all operation update service spec to reduce some factory creations - !44303 (diffs, comment 423805636)
• Trim Enterprise Edition operation controller spec to match specs from GitLab Core and reuse shared example PATCHable - !44323 (comment 425179304)
• Make use of the 🆕 expect_snowplow_event (see https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#test-snowplow-events) in operations controller specs - !44323 (comment 423861029)
• Consider adding HAML Operations Settings Show view specs for Status Page - !44574 (diffs, comment 426370086)
• Move scrubbing of the Tracing setting external_url into the presenter - !44574 (diffs, comment 425197611)
• !44823 (merged) - Unquarantine snowplow specs in operations controller spec - #259282 (comment 425243784)
• Similar to other operation settings we could add an id e.g. #js-tracing-settings and use the anchor: in project_tracing_path to link to operation settings page with the subsection already uncollapsed - !44574 (diffs, comment 426382305)

Refs #42645 (closed)