Cleanup: remove old memory atoms

Memory stats has been migrated to ProcessMemorySnapshot. This CL cleans
up the old atoms:
- remove telemetry-specific additions to ProcessMemoryState
- remove NativeProcessMemoryState atom
- move reading process cmdline under stats

Bug: 140986627
Test: atest MemoryStatUtilTest
Test: atest ProcfsMemoryUtilTest
Test: atest UidAtomTests#testProcessMemoryState
Change-Id: I5339577184d17e5cef6d657cf9b08a2fb8e75fca