Merge changes from topic "default_psi_kill_mode"

* changes:
  lmkd: Prevent killing foreground processes due to thrashing
  lmkd: Add optional kill reason description into kill reports
  lmkd: Enable new kill strategy, add and adjust required system properties
  lmkd: Use aggregate zone watermarks as low memory threshold
  lmkd: Introduce kill strategy based on zone watermarks, swap and thrashing
  lmkd: Support variable polling intervals set by event handlers
  lmkd: Change zoneinfo parsing to retrieve zone watermarks
  lmkd: Change procfs read routine to handle files larger than 1 page in size