Add standalone taskbar edu tooltip for the pinnable taskbar feature

This change adds in a standalone edu window for the pinnable taskbar
feature. The reason for the change is to educate users about pinnable
taskbar to those who have already seen taskbar edu before.

Fixes: 302589411, 300161174
Test: Went through taskbar education taskbar with the flag on and off.
Check that the standalone pinning taskbar only shows up if previous
taskbar education was already completed.
Flag:  ACONFIG com.android.launcher3.enable_taskbar_pinning DISABLED

Change-Id: I03a5fb05ae5f15892421a57355f6d503de56d9fd