Update Error Tracking Splash Page
Problem
The current splash page for Error Tracking encourages users to integrate with Sentry.
The default behavior we want is to use GitLab integrated error tracking, though we do have the challenge of integrated error tracking available only for SaaS.
Proposal
Put an updated error tracking splash page behind the same integrated_error_tracking.
feature flag. When flag is enabled, which it should be for GitLab SaaS, show the splash page that encourages users to setup integrated error tracking.