Use Slog in MR2ServiceImpl for adding logs in system logs

For testing, get system logs live with logcat, for example:
adb logcat MR2ServiceImpl:I *:S
or generate a bug report, for example:
adb bugreport
then browse the file with the Android Bug Tool UI at
go/abt-web

Bug: 259705163
Test: manually
Change-Id: If0c8bdef7afcb445f6c9b5ced60ec97d0c5bb0d7
(cherry picked from commit 6dcefe69)
Merged-In: If0c8bdef7afcb445f6c9b5ced60ec97d0c5bb0d7