Improve API test fragment and environment switching (DEV) (#1269)

* Define environment for each flavor and build type.

* Add smart LiveData class that does async initialization (not on the main thread).

* View extensions setGone/setInvisible

* Refactor test for api fragment.

* Replace ALT environment with a list to select from.

* klint

* Fix tests

* Fix tests

* Further flaky test fixes.

* Move the debug check for isLast3HourModeEnabled to the settings.
The KeyFileDownloader.kt shouldn't be aware of that detail.
The settings are what is affected by the build flavors/modes.

* Code cleanup and UI improvement of fragment_test_for_a_p_i.xml

* Code that retries flaky tests until we found a better solution.
Not great, Not terrible...

Co-authored-by: Mert Safter <mert.safter@sap.com>