Add support for late cloning

[ambarve]

This issue is created to track the merging of late cloning PRs.

Overall code changes that are required for late cloning are split into 5 stacked PRs. Each PR builds on top of the previous one. Below are the links for each of these PRs.

1. PR Add support for saving hcs compute system. #839 This PR simply adds the go wrappers required for saving a HCS compute system
   which is used during template creation.
2. PR Add support for creating cloned UVMs. #838 This PR adds the template and clone creation support in the uvm module.
3. PR Add support for creating network namespaces inside cloned uvms. #837 This PR adds the set of functions required for adding network namespace and
   network endpoints to cloned UVMs.
4. PR Add support for creating late clones via hcsshim #840 This PR adds the set of functions that expose the late cloning functionality
   from hcsshim and adds new annotations for clients to use the late cloning feature.
5. PR Add tests for late cloning #841 This PR adds several end to end tests for the late cloning feature.

These PRs can be reviewed independently but it will easier if they are reviewed in the same order. Once all 5 PRs are approved, I will merged them in reverse order i.e the branch for the 5th PR will be merged into the branch for the 4th PR and then branch for the 4th PR will be merged back into the branch for the 3rd PR and so on.

[ambarve]

@kevpar, @katiewasnothere , @dcantah, @jstarks Please review these PRs when you can. Thanks.

[kiashok]

All the PRs linked in this issue have merged. Closing this issue.