hwc/qdutils/qservice: Add dynamic idle timeout support

Add support for dynamically setting idle timeout values.
Move default idle timeout setting to IdleInvalidator.
Fix static var naming, handle errors from IdleInvalidator in hwc.
Property debug.hwc.idletime is removed with this change.

Example:
1) Set idle timeout to 100ms
adb shell service call display.qservice 16 i32 100
16 is the code for SET_IDLE_TIMEOUT, 100 is time in ms

2) Disable idle timeout
adb shell service call display.qservice 16 i32 0

Change-Id: I60e15a3ac869b4e9f4015b3be50a35c90d00d404