[Large screen] Fix searched Subsettings back navigation bug

Settings app registers SubSettings SplitPairRule with clearTop
true, it will finish Settings app if users click back button on
a SubSettings page.

This change registers SubSettings SplitPairRule with clearTop
true when users click a SubSettings item in Settings home menu.

And this change registers SubSettings SplitPairRule with clearTop
false when users click a SubSettings item in search result.

Bug: 204501750
Test: manual
      1. Settings -> Search settings -> search a SubSettings item
         (e.g., Battery)
      2. Click the searched item.
      3. Click back button.
Change-Id: I6e1862de528e971137ae7087de608bbdd79096b2