Default search engine telemetry addition

[rtestard]

User proposal

As a product manager, I want to understand how Focus iOS contributes to the business so that I can keep bringing great features to Focus.

https://github.com/mozilla-mobile/focus-ios/issues/3330 implemented most of what was needed but DS raised that we also need the default search engine.

Ideas for Solution

Implement search probes similar to Focus Android:

• Default search engine: https://dictionary.telemetry.mozilla.org/apps/focus_android/metrics/browser_default_search_engine

[Dexterp37]

@rtestard note that I'm not seeing the following as well:

• https://dictionary.telemetry.mozilla.org/apps/focus_android/metrics/browser_search_in_content
• https://dictionary.telemetry.mozilla.org/apps/focus_android/metrics/browser_search_search_count

See the related DS ticket

[razvanlitianu]

@rtestard can we create separate issues for the other 2 as well?

[rtestard]

Sure, now raised these: https://github.com/mozilla-mobile/focus-ios/issues/3478 https://github.com/mozilla-mobile/focus-ios/issues/3479

[abodea]

Verified as fixed on v 9000 (14918) with iPhone 13 Pro (15.1.1).