Move hns package out of hcsshim to its own repo

[kiashok]

• HNS package is quite independent and it can be moved out of hcsshim to its own repo.
• In k8s/k8s repo hcsshim is being imported only for using hns constructs (in 3 files only https://github.com/search?q=repo%3Akubernetes%2Fkubernetes%20%22hcsshim.%22&type=code) :
  

hcsshim tag used in k8s/k8s is more that 2-3 years old and is blocking certain updates from happening like kubernetes/kubernetes#126361 (comment)

• Also, HNS can stop depending on hcsshim release process if it is moved out to its own repo

[kiashok]

@ppereira will be working on this.

cc @msscotb @sbandari @dims @BenTheElder