* For #1063 - Adds feature flag and pref for new tab tray
* For #1063 - Swaps add tab to tab tray button when newTabTray is enabled
* For #1063 - Creates hidden preference to use new tab tray
* For #1063 - Hides tabs on home screen when setting is enabled
* For #1063 - Navigate to new tab tray from browser with setting enabled
* For #1063 - Fixes regression where we dont show the new tab message with no tabs and no collections
* For #1063 - Fixes crash when toggling to private mode on the home screen
* For #1063 - combines both settings. Cleans up lint errors
* For #5577 - Adds button to add a new search engine
* For #5577 - Adds custom engine store
* For #5577 - Creates a custom SearchEngineProvider
* For #5577 - Gives the ability to delete search engines
* For #5577 - Adds the UI to add a custom search engine
* For #5577 - Adds form to create a custom search engine
* For #5577 - Adds the ability to add a custom search engine
* For #5577 - Adds the ability to delete custom search engines
* For #5577 - Selects the first element on the add custom search engine screen
* For #5577 - Prevents adding a search engine that already exists
* For #5577 - Styles the add search engine preference
* For #5577 - Makes the name check case-insensitive
* For #5577 - Fix bug where home screen doesnt see new search engines
* For #5577 - Moves Search URL validation to its own type
* For #5577 - Fixes linting errors
* For #5577 - Adds the ability to edit a custom search engine
* For #5577 - Allows the user to edit a serach engine even when it is the last item in the list
* For #5577 - Adds an undo snackbar when deleting a search engine
* For #5577 - Moves all of the strings to be translated
* For #5577 - Fixes bug when deleting your default search engine
* For #5577 - Puts adding search engines behind a feature flag
* For #5577 - Navigate to custom search engine SUMO article when tapping learn more
* For #5577 - Fixes nits
* For #5577 - Uses concept-fetch to validate search string
* For #5577 - Adds string resources for the cannot reach error state
