tools: acrn-crashlog: channel module for acrnprobe

The channel represents a way of detecting the system's events.
So far, there are 3 channels:
1. oneshot, detect once while acrnprobe startup.
2. polling, run a detecting job with fixed time interval.
3. inotify, watch the change of file or dir.

Signed-off-by: Liu Xinwu <xinwu.liu@intel.com>
Reviewed-by: Zhang Yanmin <yanmin.zhang@intel.com>
Reviewed-by: Liu Chuansheng <chuansheng.liu@intel.com>
Reviewed-by: Zhao Yakui <yakui.zhao@intel.com>
Reviewed-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>
Acked-by: Eddie Dong <Eddie.dong@intel.com>