HeadsUpUtil: Log TAG_CLICKED_NOTIFICATION changes

We're trying to fix a bug where HUNs don't disappear properly when
tapped, and we've got a cause identified, but the fix throws a bit of a
wrench into the animations.

This tag is useful information about how the animations are behaving, so
log changes to it.

Bug: 249840069
Test: manual
Change-Id: I4d912223aafeba628c9420bb7b2a64850d6c79ca