* For #11664 — Fixup MissingResourceExceptions being thrown in exotic Locales (#13124)

Our kotlin code is not catching the `MissingResourceException` in the `LeanplumMetricsService` which results in the app crashing when the locale isn't known by the device.

Catches the exception, and falls back to the ISO 639 language code. This isn't a great solution, because ISO 639 isn't especially stable.

In practice however this is almost certainly never going to be a problem because Leanplum isn't going to be supported in such exotic locales.

In this case, using the ISO 639 language code allows the error message to be more informative.

* For #13117 - Hide save to collection button for private tabs in tab tray

Co-authored-by: jhugman <jhugman@users.noreply.github.com>
Co-authored-by: ekager <ekager@mozilla.com>