Skip nav button animation in gesture nav mode

- Also removed unused rotation button code
- Skip adding certain property holders in phone mode
- Update FLAG_SMALL_SCREEN value from isPhoneButtonNavMode to isPhoneMode, so that it's more aligned with what the name suggests (it shouldn't affect the functionality regardless as the view is invisible in small screen)

Based on https://b.corp.google.com/issues/361593564#comment4

Bug: 361593564
Test: manual
Flag: EXEMPT bugfix
Change-Id: I1de7fa061a6c6aba9f949a0bcf8cfced84273e3f

quickstep/src/com/android/launcher3/taskbar/TaskbarViewController.java

@@ -219,8 +219,8 @@ public class TaskbarViewController implements TaskbarControllers.LoggableTaskbar
         if (ENABLE_TASKBAR_NAVBAR_UNIFICATION) {
             // This gets modified in NavbarButtonsViewController, but the initial value it reads
             // may be incorrect since it's state gets destroyed on taskbar recreate, so reset here
-            mTaskbarIconAlpha.get(ALPHA_INDEX_SMALL_SCREEN)
-                    .animateToValue(mActivity.isPhoneButtonNavMode() ? 0 : 1).start();
+            mTaskbarIconAlpha.get(ALPHA_INDEX_SMALL_SCREEN).setValue(
+                    mActivity.isPhoneMode() ? 0 : 1);
         }
         if (enableTaskbarPinning()) {
             mTaskbarView.addOnLayoutChangeListener(mTaskbarViewLayoutChangeListener);