common : improve per-app memory usage calculation

common : improve per-app memory usage calculation

1) New functions provide per-process memory usage
  - pss, uss : use totmaps(if supported) or smaps(else)
  - zram usage
  - memory usage : pss + vmswap

2) proc_get_mem_usage is modified
  - VmSize, VmRSS -> VmSwap, VmRSS

3) Other modules use these functions above
  - vmpressure no more uses HEART-memory to get uss
  - Signal handlers providing memory usage reply not rss but (pss + vmswap)

Change-Id: If8e2ff575b8d666ae82317228ff821c157c5cfc2
Signed-off-by: Kichan Kwon <k_c.kwon@samsung.com>