Fix IMS window visibility

Fixes an issue with IMS window visibility, where an unfortunate timing
of removeImeSurface() and showWindow() could result in the window being
hidden without resetting mDecorViewVisible.

Root cause is the scheduled removeImeSurface() not being cancelled in
all code paths that end up calling showWindow().

To avoid this we
- consolidate calls to cancelImeSurfaceRemoval
  and applyVisibilityInInsetsConsumerIfNecessary into showWindow()
- inline the now unnecessary doHideWindow
- unconditionally call mWindow.show() in showWindow, since View.java
  already avoids unnecessary work if the decor visibility won't change

Fixes: 203137087
Test: manual
Change-Id: Iaef9efd4f1a89fe6da27fc6396b62ff3b4ca11f4