Introduce new atom to replace existing ProcessMemoryState and NativeProcessMemoryState ones for telemetry purposes. This change is the first step to decouple memory stats from the framework internals. Follow-up CLs will remove the telemetry parts from the existing atoms. Test: atest ProcfsMemoryUtilTest Test: statsd_testdrive 10064 Change-Id: I7959c6e473201c10e7da17fa49d864bb03a2403c