Keep reporting > 0 insets on home screen

Technically mControllers.stashedHandleViewController.isStashedHandleVisible() is false on the home screen (since we unstash), so now we also check isInApp(). This ensures that we always return the same insets when on the home screen - and the insets we report are the same as when you launch an app, to ensure seamless transitions. The value itself shouldn't matter to launcher as long as it is static, since launcher overrides the insets due to taskbar anyway, but we need to keep the value static to avoid configuration change.

Test: Open a website in Chrome, stash taskbar, then launch Chrome from home screen and ensure content doesn't jump during the transition
Fixes: 221238308
Change-Id: I81e320b3a8d32ffe78441be5dd8f15a586d3b842