Updates oci image config to support upstream ArgsEscaped

ArgsEscaped has now been merged into upstream OCI image spec.
This change removes the workaround we were doing in containerd
to deserialize the extra json outside of the spec and instead
just uses the formal spec types.

Signed-off-by: Justin Terry <jlterry@amazon.com>

vendor/github.com/opencontainers/image-spec/specs-go/v1/manifest.go

@@ -1,4 +1,4 @@
-// Copyright 2016 The Linux Foundation
+// Copyright 2016-2022 The Linux Foundation
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -30,6 +30,9 @@ type Manifest struct {
 	// Layers is an indexed list of layers referenced by the manifest.
 	Layers []Descriptor `json:"layers"`
 
+	// Subject is an optional link from the image manifest to another manifest forming an association between the image manifest and the other manifest.
+	Subject *Descriptor `json:"subject,omitempty"`
+
 	// Annotations contains arbitrary metadata for the image manifest.
 	Annotations map[string]string `json:"annotations,omitempty"`
 }