Fix launcher animates keyboard by wrong insets visible value

Remove ActivityRecord#mLastImeShown in
InsetsPolicy#adjustVisibilityForIme. In case when the launcher has
requested to hide keyboard when launching the next app, after
backing to launcher from the app, the launcher still took the
wrong IME visiblity from WindowInsetsController#isVisible(ime()) to
show the keyboard again.

Fix: 254624767
Test: atest WindowStateTests
Test: atest KeyboardVisibilityControlTest
Test: manual as steps:
   1) Enable 3-button navigations
   2) enable 'Always show keyboard' on home settings
   3) Go to all-apps, open an app while the keyboard is visible
   4) Close the app with the central button of 3-button navigation
   5) Expect the keyboard won't be shown after backing to home

Change-Id: I3c9e3573454b26bc5f8e4cda90f9dc45eadae74c