Move statsd metadata from statslog to atoms_info

Clients don't need to know about statsd metadata. Extract out metadata
from statslog.h/cpp into atoms_info.h/cpp which is only used by statsd.

Generated atoms_info.h: https://paste.googleplex.com/6303016724463616
Generated atoms_info.cpp: https://paste.googleplex.com/5717940978581504

Test: m -j
Test: old metadata in statslog matches the metadata in
atoms_info
Test: Flashes successfully
Test: adb logcat "*:S statsd:*"

Change-Id: I56ef3cc4ea1fbd2cd0130d4e9576b242efb9f627
Merged-In: I56ef3cc4ea1fbd2cd0130d4e9576b242efb9f627