[Rollouts] Add integration test app

[themiswang]

Adding integration test app
Right now added 4 targets:

• Neither Crash nor RC integration
• Either one of Crash or RC integration
• Both Crash and RC integration

To run the test app:

• gcert your local machine
• run ./generate_featureRolloutsTestsApp.sh

Console app: https://firebase-console-ci.corp.google.com/u/0/project/feature-rollouts-test-app/settings/general/ios:com.firebase.config.featureRolloutsTestApp

#no-changelog

[themiswang]

Has a interface for Crash testing. For RC side will add later if needed.

[themiswang]

screen shot: https://screenshot.googleplex.com/3Y6EbtsbkEzyTHm

[danasilver]

Just jotting down some notes for future me:

Had to swap the Ruby version in .ruby-version to 2.7.6 (installed via rbenv).

Script is in FirebaseRemoteConfig so:

gcert
./FirebaseRemoteConfig/generate_featureRolloutsTestApp.sh

Then just ran the app in Xcode and everything worked 🎈

[themiswang]

Just jotting down some notes for future me:

Had to swap the Ruby version in .ruby-version to 2.7.6 (installed via rbenv).

Script is in FirebaseRemoteConfig so:

gcert
./FirebaseRemoteConfig/generate_featureRolloutsTestApp.sh

Then just ran the app in Xcode and everything worked 🎈

In case anyone need a ruby version control, here is a blog for that: https://www.moncefbelyamani.com/how-to-install-xcode-homebrew-git-rvm-ruby-on-mac/