Signed-off-by: PingWang <wang.ping5@zte.com.cn>

Add docs
Signed-off-by: PingWang <wang.ping5@zte.com.cn>

add docs for ExtenderFilterResult.FailedNodes in types.go
Signed-off-by: PingWang <wang.ping5@zte.com.cn>

Modify the extender.Filter test.
Signed-off-by: PingWang <wang.ping5@zte.com.cn>

Update extender_test.go
Signed-off-by: PingWang <wang.ping5@zte.com.cn>

modify the comments
Signed-off-by: PingWang <wang.ping5@zte.com.cn>

gofmt -s scheduler_interface.go
Signed-off-by: PingWang <wang.ping5@zte.com.cn>

update the comments
Signed-off-by: PingWang <wang.ping5@zte.com.cn>