Remove nonOverlappingTaskarInsets

- Override our insets in LauncherRootView to explicitly only care about nav bar size, ignoring any insets due to taskbar.
- Previously we used nonOverlappingTaskbarInsets to belatedly subtract from measurements in e.g. DeviceProfile, but now we can revert most of those calculations since we effectively subtract taskbar insets at the root.

Test: visual in different orientations and navigation modes, and testPressHomeOnAllAppsContextMenu to ensure REQUEST_WINDOW_INSETS still works for automated tests
Fixes: 200607741
Change-Id: I8de5a268c686a1354b4beaa30e101bab6bed5af9