Cancel future HUN lifetime extension after action press

ag/18595495 made sure that action presses *after* a HUN's lifetime was
extended would shorten the lifetime extension to the minimum display
time, but noted that race conditions were possible.

This change makes sure that action presses *before or after* a HUNning
notification's removal will *prevent or end* lifetime extension
entirely.

Bug: 233864220
Bug: 284418902
Test: atest HeadsUpManagerTest HeadsUpCoordinatorTest
Change-Id: Ib751cfe29e994df5582186cb8d9cf91f0977a518