system: initial dmesgd implementation am: 93b854f8e9 am: df1051cce2 am: ee172ad09f am: 08da80cdd9

Original change: https://android-review.googlesource.com/c/platform/system/dmesgd/+/1974479

Change-Id: I8debb102a4601d16c6fd21f047de015d19998cec