Add sandbox specs along with methods for serialization and deserialization into UVM options

[rawahars]

Summary

In this PR, we are adding the proto definition which declares the specs used to create a sandbox by shim. Additionally, we have added the methods Generate and BuildUVMOptions which are used for serialization and deserialization.

In the Generate method, all the annotations as passed by the client are parsed and the appropriate fields are set in the specs.
In the BuildUVMOptions method, all the fields as set in the Specs are parsed and are set into the OptionsLCOW or OptionsWCOW instance which is then used to create the UVM.

This will be the defacto method going forward-

• CRI calls the Generate method in RunPodSandbox to generate the sandbox specs.
  Alternatively, for legacy workflows using pause sandbox where the sandbox is created via Task API, the shim will call Generate method in the Create call.
• CreateSandbox call will invoke BuildUVMOptions on the Specs to generate the UVMOptions.
  Alternatively, for legacy workflows, the same will be called in the Create call of Task API.
• The UVM options are used to create the UVMs by HCS.

These methods encapsulate the logic as present in

hcsshim/internal/oci/uvm.go

Line 349 in 73fdc96

func SpecToUVMCreateOpts(ctx context.Context, s *specs.Spec, id, owner string) (interface{}, error) {

We hope to deprecate the SpecToUVMCreateOpts method and encapsulate the parsing logic in above methods.

Changes introduced in this PR

• Added the proto for sandbox Specs
• Added sandbox_specs.go which includes the Generate method to create the specs.
• Added uvm_specs.go which includes the BuildUVMOptions method to create the UVM options from the specs.
• Added extensive unit tests for both the files above.
• Changes in internal\oci package for code reusability in the new code.

Tests

• Unit tests have been added which covers the parsing logic extensively.