Rename InputWindowHandle hasFocus to focusable

A window with hasFocus set to true, means the window can be focusable.
The current name is confusing when mutliple windows set the field to
true. Rename this to focusable and also remove canRecieveKeys field which
is not used.

Test: presubmit
Bug: 151179149
Change-Id: I38f63dfd08300b6fc97388ee6d8bcbdddb89c4a1
diff --git a/include/input/InputWindow.h b/include/input/InputWindow.h
index 8a752c1..7372022 100644
--- a/include/input/InputWindow.h
+++ b/include/input/InputWindow.h
@@ -167,8 +167,7 @@
      */
     Region touchableRegion;
     bool visible = false;
-    bool canReceiveKeys = false;
-    bool hasFocus = false;
+    bool focusable = false;
     bool hasWallpaper = false;
     bool paused = false;
     /* This flag is set when the window is of a trusted type that is allowed to silently