Show all nav buttons when IME showing

* Keep home and recents button, and rotate back button
to be down when IME shows in 3 button task bar.
* Move IME switcher to left side of taskbar for 3 button,
keep on right side for gesture nav.

Bug: 191399224
Test: Tested RTL and LTR, gesture + button nav
with and w/o IME.

Change-Id: I7959d26986e546596e2436b8b5eb7668f44b55cf
diff --git a/quickstep/res/layout/taskbar.xml b/quickstep/res/layout/taskbar.xml
index b4c168c..83ad9f3 100644
--- a/quickstep/res/layout/taskbar.xml
+++ b/quickstep/res/layout/taskbar.xml
@@ -52,6 +52,7 @@
             android:orientation="horizontal"
             android:paddingLeft="@dimen/taskbar_nav_buttons_spacing"
             android:paddingRight="@dimen/taskbar_nav_buttons_spacing"
+            android:layout_marginEnd="@dimen/taskbar_contextual_button_margin"
             android:gravity="center_vertical"
             android:layout_gravity="end"/>