Refactor FXIOS-10855 #23671 Change rating prompt request threshold (backport #24523)

[mergify]

📜 Tickets

Jira ticket
Github issue

💡 Description

Adjusting the rating prompt thresholds before we release it next week

📝 Checklist

You have to check all boxes before merging

• Filled in the above information (tickets numbers and description of your work)
• Updated the PR name to follow our PR naming guidelines
• Wrote unit tests and/or ensured the tests suite is passing
• When working on UI, I checked and implemented accessibility (minimum Dynamic Text and VoiceOver)
• If needed, I updated documentation / comments for complex code and public methods
• If needed, added a backport comment (example @Mergifyio backport release/v120)

---

This is an automatic backport of pull request #24523 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of b7217ee has failed:

On branch mergify/bp/release/v135/pr-24523
Your branch is up to date with 'origin/release/v135'.

You are currently cherry-picking commit b7217ee09.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   firefox-ios/Client/CrashTracker.swift
	modified:   firefox-ios/Client/FeatureFlags/NimbusFlaggableFeature.swift
	modified:   firefox-ios/Client/Nimbus/NimbusFeatureFlagLayer.swift
	new file:   firefox-ios/firefox-ios-tests/Tests/ClientTests/Helpers/CrashTrackerTests.swift
	new file:   firefox-ios/firefox-ios-tests/Tests/ClientTests/Mocks/MockCrashTracker.swift
	new file:   firefox-ios/nimbus-features/ratingPromptFeature.yaml
	modified:   firefox-ios/nimbus.fml.yaml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   firefox-ios/Client.xcodeproj/project.pbxproj
	both modified:   firefox-ios/Client/Frontend/Browser/BrowserViewController/Views/BrowserViewController.swift
	both modified:   firefox-ios/Client/RatingPromptManager.swift
	both modified:   firefox-ios/firefox-ios-tests/Tests/ClientTests/Helpers/RatingPromptManagerTests.swift

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[lmarceau]

@rvandermeulen we need #24272 merged before we can merge this PR (hence the conflicts). Those two PRs needs to ship at the same time since the current PR adds the possibility to control the change with an experiment.

[lmarceau]

LGTM

[rvandermeulen]

Approved for 135.1