[flexiglass] Anchor dual shade tooltips to their elements

Properly sources the position of the elements that the educational
tooltips are anchored to, from the actual elements themselves.

Bug: 406213664
Test: manually verified that the tooltips are properly anchored
Flag: com.android.systemui.scene_container
Change-Id: I125e3b998921cf793cbed83713fc299e0314b62b