[Menu][A11y] Fix context menu keyboard controls in Menu demo

Previously, pressing Enter on the context menu TextView in the menu demo would incorrectly open the menu. Additionally, pressing Ctrl+Enter would open the menu as a dialog, inconsistent with the floating menu style seen on long-press.

This change updates the OnKeyListener to:

Ignore Enter/DPAD_CENTER/Space key presses unless Ctrl is also held down.
When Ctrl+Enter is detected on API 24+, use showContextMenu(x, y) to display the menu as a floating menu centered on the view. This aligns its appearance with the long-press behavior.
On API < 24, fall back to showContextMenu(), which displays the menu as a dialog.

PiperOrigin-RevId: 806198204

Author: Material Design Team

catalog/java/io/material/catalog/menu/MenuMainDemoFragment.java

@@ -104,10 +104,25 @@ private void setupContextMenuWithKeyboard(View view) {
     registerForContextMenu(view);
     view.setOnKeyListener(
         (v, keyCode, event) -> {
-          if (event.getAction() == KeyEvent.ACTION_DOWN
-              && event.isCtrlPressed()
-              && (keyCode == KeyEvent.KEYCODE_ENTER || keyCode == KeyEvent.KEYCODE_DPAD_CENTER)) {
-            v.showContextMenu();
+          if (event.getAction() != KeyEvent.ACTION_DOWN) {
+            return false;
+          }
+
+          if (keyCode == KeyEvent.KEYCODE_SPACE) {
+            return true;
+          }
+
+          if (keyCode == KeyEvent.KEYCODE_ENTER || keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
+            if (event.isCtrlPressed()) {
+              // Use showContextMenu(x, y) to show the context menu as a floating menu
+              // on newer Android versions, similar to long-press. Fall back to
+              // showContextMenu() on older versions, which will appear as a dialog.
+              if (VERSION.SDK_INT >= VERSION_CODES.N) {
+                v.showContextMenu(v.getWidth() / 2f, v.getHeight() / 2f);
+              } else {
+                v.showContextMenu();
+              }
+            }
             return true;
           }
           return false;