[reset] Call SearchUiManager#resetSearch instead of reset.

This is a follow-up of ag/26362927.
When it's in searching state, we only need to reset search instead of resetting everything.

Test: search something and scroll in AA+. Trigger AA+ by filing an intent (adb shell am start -n com.google.android.apps.nexuslauncher/.NexusLauncherActivity -a android.intent.action.ALL_APPS). Notice the search RV is reset and scroll to top.
Bug: 328505782
Flag: aconfig com.android.launcher3.enable_private_space nextfood
Change-Id: I9d1d4386077433a676c1f3b8e3614fb848284a88