Cleanup the code to remove the experiments and use new feature flags

[anikiki]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1200581511062568/task/1210824886441068?focus=true

Description

Refactored the widget-related experiment implementation by replacing the experiment-based approach with feature toggles.

1. Removing OnboardingHomeScreenWidgetExperiment and PostCtaExperienceExperiment classes and their implementations
2. Updating the OnboardingHomeScreenWidgetToggles and PostCtaExperienceToggles interfaces to use simple feature toggles
3. Removing experiment-related pixel tracking and metrics collection
4. Updating the widget-related functionality to use the new toggle-based approach
5. Renaming and moving files for clarity

The PR removes complex experiment tracking code and replaces it with a more straightforward feature toggle implementation, making the codebase more maintainable and easier to understand.

Steps to test this PR

• Fresh install from this branch.
• Don't skip onboarding. Go through the pre-onboarding and once you can access the Settings, override the privacy config with this one: https://www.jsonblob.com/api/1415374897584201728
• Continue with onboarding until you see the last Dax dialog (the one with the wings). Close it.
• Open a new tab and confirm you see the widget prompt as in the left screenshot (Onboarding widget prompt).
• Go to Settings.
• Tap on the "Home Screen Widget", last option in the "Protections" section at the top. Confirm you see the widget prompt as in the right screenshot (Settings widget prompt).

NO UI changes, reference screenshots

Onboarding widget prompt	Settings widget prompt

[anikiki]

• Cleanup the code to remove the experiments and use new feature flags #6777 👈 (View in Graphite)
• develop

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[Copilot]

Pull Request Overview

Refactored the widget experiment infrastructure by replacing experiment-based approach with feature toggles. This cleanup removes complex experiment tracking code and introduces simpler toggle-based implementations.

• Removed experiment classes and their tracking infrastructure
• Migrated to feature toggle-based widget control
• Updated all dependencies to use new toggle interfaces

Reviewed Changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
SystemSearchViewModel.kt	Removed widget experiment tracking calls and constructor dependencies
SettingsViewModel.kt	Replaced experiment with toggle-based widget prompt detection
CtaViewModel.kt	Updated to use toggle interface instead of experiment class
SearchWidgetLifecycleDelegate.kt	Removed experiment tracking from widget lifecycle methods
BrowserTabFragment.kt	Updated import and dialog class name references
PostCtaExperienceToggles.kt	New toggle interface for post-CTA experience features
OnboardingHomeScreenWidgetToggles.kt	New toggle interface for onboarding widget features
AlternativeHomeScreenWidgetBottomSheetDialog.kt	Moved and renamed dialog class with corrected imports
Test files	Updated all test files to use new toggle interfaces instead of mock experiments

[landomen]

Great cleanup and works as expected 🙌