Update github.com/opencontainers/runtime-tools to v0.6.0

Also add new dependencies on github.com/xeipuuv/gojson* (brought up by
new runtime-tools) and adapt the containerd/cri code to replace the APIs
that were removed by runtime-tools.

In particular, add new helpers to handle the capabilities, since
runtime-tools now split them into separate sets of functions for each
capability set.

Replace g.Spec() with g.Config since g.Spec() has been deprecated in the
runtime-tools API.

Signed-off-by: Filipe Brandenburger <filbranden@google.com>

vendor/github.com/opencontainers/runtime-tools/specerror/runtime-linux.go

@@ -0,0 +1,23 @@
+package specerror
+
+import (
+	"fmt"
+
+	rfc2119 "github.com/opencontainers/runtime-tools/error"
+)
+
+// define error codes
+const (
+	// DefaultRuntimeLinuxSymlinks represents "While creating the container (step 2 in the lifecycle), runtimes MUST create default symlinks if the source file exists after processing `mounts`."
+	DefaultRuntimeLinuxSymlinks Code = 0xf001 + iota
+)
+
+var (
+	devSymbolicLinksRef = func(version string) (reference string, err error) {
+		return fmt.Sprintf(referenceTemplate, version, "runtime-linux.md#dev-symbolic-links"), nil
+	}
+)
+
+func init() {
+	register(DefaultRuntimeLinuxSymlinks, rfc2119.Must, devSymbolicLinksRef)
+}