[SB][Chips] Keep track of each chip's current on-screens bounds.

This will let us do a nice chip-to-HUN animation where the HUN animates
starting from the chip bounds.

Bug: 393369891
Test: Verified via logging that non-chip HUNs have no bounds passed to
NSSL, and chip HUNs *do* have bounds passed to NSSL
Test: atest OngoingActivityChipsWithNotifsViewModelTest
Test: With flag disabled, verify chip-to-HUN animation still starts
under the status bar

Flag: com.android.systemui.status_bar_chip_to_hun_animation

Change-Id: Iee4f496c94c3ca4a34cad992903a1741b3833c88