plugin-api: resourced: Add a skeleton of get_kill_candidates_post funcs

plugin-api: resourced: Add a skeleton of get_kill_candidates_post funcs

Add a skeleton of three get_kill_candidates_post funcs. These functions
are directly mapped to get_kill_candidates_post funcs in resourced backend.

Support LMK governor post funcs which will be called after
LMK governor function to reorder a victim candidate list

resourced supports three type of get_kill_candidates_post ops newly
  - int syscommon_plugin_resourced_memory_lmk_get_kill_candidates_post(
		  GArray *candidates)
    to consider user custom governor policy
  - int syscommon_plugin_resourced_memory_lmk_get_kill_candidates_post_with_wss(
		  GArray *candidates)
    to consider working set size of app
  - int syscommon_plugin_resourced_memory_lmk_get_kill_candidates_post_with_foreground(
		  GArray *candidates)
    to consider window information of app

Change-Id: I2a3c42635ce105f4400a68c8c382fb6548a11f8e
Signed-off-by: Unsung Lee <unsung.lee@samsung.com>