[MOB-4300] Implement Omnibox

[kimar]

MOB-4300

Context

Work in Progress

Implements iOS Omnibox.

Approach

Other

Before merging

Checklist

• I performed some relevant testing on a real device and/or simulator for both iPhone and iPad
• I wrote Unit Tests that confirm the expected behaviour
• I updated only the english localization source files if needed
• I added the // Ecosia: helper comments where needed
• I made sure that any change to the Analytics events included in PR won't alter current analytics (e.g. new users, upgrading users)
• I included documentation updates to the coding standards or Confluence doc, when needed