[Large sceen] Don't go Settings 2-pane deep link flow if not task root

When a full screen or a non-Settings-app ActivityA starts ActivityB of
a SettingsActivity, splitInfos will be empty and it unexpectedly goes
Settings 2-pane deep link flow.

This change checks if an Activity is not task root, don't go Settings
2-pane deep link flow.

Bug: 205497007
Test: manual
      SUW -> Vision settings
      Check if it goes Settings 2-pane deep link flow.
Change-Id: I0822fbe71fdde47ce7c070986371a4dfea84992c

src/com/android/settings/SettingsActivity.java

@@ -370,8 +370,9 @@ public class SettingsActivity extends SettingsBaseActivity
         final SplitStateObserver splitStateObserver = new SplitStateObserver(this /* activity*/,
                 true /* listenOnce */,
                 splitInfos -> {
-                    if (!splitInfos.isEmpty()) {
+                    if (!splitInfos.isEmpty() || !SettingsActivity.this.isTaskRoot()) {
-                        // It's already in 2-pane and no need to go 2-pane deep link flow.
+                        // It's already in 2-pane or in a non-empty task, there is no need to go
+                        // 2-pane deep link flow.
                         return;
                     }