Handle BT hearing device event history for HaTS surveys

We'll run surveys on hearing adis and general hearing devices users to
know the satisfaction difference between different kinds of devices.
This can help us prioritize to improve the parts which are less satisfying.

Bug: 294627726
Test: atest HearingAidStatsLogUtilsTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:070e0055b2121f8cd0c42873b66b18fd778f7661)

Change-Id: I00280ddfcd11f3688c6c3e626cdae4914c5eb887