XsWack

this PR introduce a user-facing change， please update the info

also we should update the doc to instruct users how to use list-watch

```Fix log path to /var/log/kubeedge/edgecore.log``` I do not see any changes about this

> don't change the edgecore log path, it seems that edgecore log path has always been /etc/kubeedge/kubeedge/edge/edgecore.log > > https://github.com/kubeedge/kubeedge/blob/a6a243ca1f0d305f2c9d03400fae2f7e1629825b/keadm/cmd/keadm/app/cmd/util/common.go#L463-L469 ok， please update the the pr title to reflect what...

lgtm

/cc @zhu733756 @fisherxu

cc @RyanZhaoXB

`Is there any test or numerical value to show the performance of the cache ability?` I do not know what you mean by this? what performance do you care about?

@zc2638 Could you take a look at this, thanks

cc @gy95