Make logging optional when checking for heads up

This adds a new method, checkHeadsUp, to be used for cases where we just want to check whether something *would* heads up but not log it (because checking this for a lot of notifications at once, it'll spuriously log).

Bug: 248325248
Test: manual
Change-Id: I5499e03d46c6cac2934af9532b4984646b3bb69f