Insights - Mobile Screens

[markushi]

A mobile module providing an entry point, top level metrics and the ability to drill deeper into app starts, screen loads and UI jank.

Internal notion doc for feedback here. Development branch here.

### Tasks GA
- [x] Add platform switcher for RN projects
- [x] Remove screens label
- [x] Sub-Modules: Fix padding
- [x] Sub-Modules: Have proper routing
- [x] Add missing columns in overview table
- [ ] Add release selectors
- [ ] Add product docs for Screen Rendering module
- [ ] Add product docs for Mobile Screens landing page
- [ ] Update existing Mobile modules docs pages (mainly screenshots)
- [ ] Update sales
- [ ] Switch to ratios for slow and frozen frame - https://github.com/getsentry/sentry/issues/75317
- [ ] (Backend) Fix missing unit for frame delay
- [ ] Switch to ratio for frame delay - https://github.com/getsentry/sentry/issues/75318
- [ ] Add platform specific threshold, define thresholds for frame metrics (frozen / slow / delay) (get rid of grey bars)
- [ ] Ensure existing app-start / screen load pages are properly redirected (including breadcrumbs)
- [ ] Implement empty state logic

### Tasks Post-GA
- [ ] Add tooltips for table columns to clearly explain what they represent.
- [ ] (Ensure new screens are being tracked)
- [ ] Change column: Switch to dashes instead of 0% in case the change is ~0

[getsantry[bot]]

Routing to @getsentry/product-owners-insights for triage ⏲️