Fix androidTest

This MR updates the androidTest code to work with the Ceno Browser. Some notable changes include,

• Removed any tests related to Firefox accounts, as those were irrelevant to Ceno
• Added an OnboardingRobot.kt to skip through the onboarding fragments before every test. This should be expanded to fully test the OnboardingSequence on that UI is finalized.
• Significant changes to SettingsViewTest and ThreeDotMenuTest to, at a minimum, test that all menu items added for Ceno are properly displayed, additional work required to verify full functionality of all menu items.
• Disabled CustomTabsTest, MediaPlaybackTest and ReaderView as they are completely supported by Ceno on every version of Android, new bugs should be opened for each of these to track progress on implementing and testing these features.
• Modifies the TabTrayMenuTest to support Ceno's homepage behavior (i.e. that the homepage is a real tab).

With these changes, 37 or the 42 test pass reliably and only 5 are skipped (the aforementioned disabled tests). This a solid baseline for fixing the remaining tests (which are largely dependent on implementing the features they test) and writing new tests to verify the behavior of Ceno-specific features.

After this is merged, we can consider #5 (closed) complete. New issues should be opened for remaining tests and ideas for new tests.