Fix alarms being posted on wrong thread

Alarms from btu_bta_alarm_queue and btu_generic_alarm_queue should be
processed on the main MessageLoop thread.
Replaced obsoleted alarm_set_on_queue() alarm API with the new
alarm_set_on_mloop() API

Test: manual
Bug: 65078753
Change-Id: I54b472b39b44a6c541dbdcdad7414056d0dd4163
Merged-In: I54b472b39b44a6c541dbdcdad7414056d0dd4163
(cherry picked from commit 01a63882)