Clean up visibility related flags in ActivityRecord

- Replace visible and hiddenRequested flag by a single flag
  mVisibleRequested.
- Merge setVisible() into setVisiblity().

Test: Refactoring, all existing tests pass.
Bug: 80414790
Change-Id: I7bafdb86e6b8431046775d3968d24f85c3fac45a
diff --git a/services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java b/services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java
index 571f214..924a194 100644
--- a/services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java
@@ -394,7 +394,7 @@
         assertEquals(window1, mWm.mRoot.getTopFocusedDisplayContent().mCurrentFocus);
 
         // Make sure top focused display not changed if there is a focused app.
-        window1.mActivityRecord.hiddenRequested = true;
+        window1.mActivityRecord.mVisibleRequested = false;
         window1.getDisplayContent().setFocusedApp(window1.mActivityRecord);
         updateFocusedWindow();
         assertTrue(!window1.isFocused());