Separate ipvlan/macvlan/pure/bridge CNI plugin

[chenchun]

Those plugins are currently mixing in https://github.com/tkestack/galaxy/blob/master/cni/k8s-vlan/k8s_vlan.go which makes them hard to maintain or to add new feature.

It's better to deprecate the old one first and adding each of ipvlan/macvlan/pure/bridge as a new plugin. We can eventually remove the old one when we have all clusters upgraded at future.

[chenchun]

Pure plugin is done in https://github.com/tkestack/galaxy/pull/67