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

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

Change-Id: I66b94987e54ffed1f38bd4c1b41e1ae2c0f319f1