Revert^2 "[hotword] remove exemption for pixel devices"

Reason for revert: Re-applying with test fixes

Reverted changes: /q/submissionid:23245838-revert-23212396-hotword_exemption_sysprop-TQLSORBLKC

Bug: 279405774

Test: atest HotwordDetectionServiceBasicTest
HotwordAudioEgressEventReportedStatsTest on a cuttlefish instance

Change-Id: Icffa88c7c7c616b6f906fc95fa98d09c75cfe677