Sandbox: Add SandboxMetrics rpc

To gather metrics/stats about a specific sandbox instance, it'd be nice to
have a dedicated rpc for this. Due to the same "what kind of stats are going
to be returned" dilemma exists for sandboxes as well, I've re-used the metrics
type we have as the data field is just an `any`, leaving the metrics returned
entirely up to the shim author. For CRI usecases this will just be cgroup and
windows stats as that's all that's supported right now.

Signed-off-by: Danny Canter <danny@dcantah.dev>

api/next.pb.txt

@@ -884,6 +884,42 @@ file {
   }
   syntax: "proto3"
 }
+file {
+  name: "github.com/containerd/containerd/api/types/metrics.proto"
+  package: "containerd.types"
+  dependency: "google/protobuf/any.proto"
+  dependency: "google/protobuf/timestamp.proto"
+  message_type {
+    name: "Metric"
+    field {
+      name: "timestamp"
+      number: 1
+      label: LABEL_OPTIONAL
+      type: TYPE_MESSAGE
+      type_name: ".google.protobuf.Timestamp"
+      json_name: "timestamp"
+    }
+    field {
+      name: "id"
+      number: 2
+      label: LABEL_OPTIONAL
+      type: TYPE_STRING
+      json_name: "id"
+    }
+    field {
+      name: "data"
+      number: 3
+      label: LABEL_OPTIONAL
+      type: TYPE_MESSAGE
+      type_name: ".google.protobuf.Any"
+      json_name: "data"
+    }
+  }
+  options {
+    go_package: "github.com/containerd/containerd/api/types;types"
+  }
+  syntax: "proto3"
+}
 file {
   name: "github.com/containerd/containerd/api/runtime/sandbox/v1/sandbox.proto"
   package: "containerd.runtime.sandbox.v1"
@@ -891,6 +927,7 @@ file {
   dependency: "google/protobuf/timestamp.proto"
   dependency: "github.com/containerd/containerd/api/types/mount.proto"
   dependency: "github.com/containerd/containerd/api/types/platform.proto"
+  dependency: "github.com/containerd/containerd/api/types/metrics.proto"
   message_type {
     name: "CreateSandboxRequest"
     field {
@@ -1199,6 +1236,27 @@ file {
   message_type {
     name: "ShutdownSandboxResponse"
   }
+  message_type {
+    name: "SandboxMetricsRequest"
+    field {
+      name: "sandbox_id"
+      number: 1
+      label: LABEL_OPTIONAL
+      type: TYPE_STRING
+      json_name: "sandboxId"
+    }
+  }
+  message_type {
+    name: "SandboxMetricsResponse"
+    field {
+      name: "metrics"
+      number: 1
+      label: LABEL_OPTIONAL
+      type: TYPE_MESSAGE
+      type_name: ".containerd.types.Metric"
+      json_name: "metrics"
+    }
+  }
   service {
     name: "Sandbox"
     method {
@@ -1241,6 +1299,11 @@ file {
       input_type: ".containerd.runtime.sandbox.v1.ShutdownSandboxRequest"
       output_type: ".containerd.runtime.sandbox.v1.ShutdownSandboxResponse"
     }
+    method {
+      name: "SandboxMetrics"
+      input_type: ".containerd.runtime.sandbox.v1.SandboxMetricsRequest"
+      output_type: ".containerd.runtime.sandbox.v1.SandboxMetricsResponse"
+    }
   }
   options {
     go_package: "github.com/containerd/containerd/api/runtime/sandbox/v1;sandbox"
@@ -5944,42 +6007,6 @@ file {
   }
   syntax: "proto3"
 }
-file {
-  name: "github.com/containerd/containerd/api/types/metrics.proto"
-  package: "containerd.types"
-  dependency: "google/protobuf/any.proto"
-  dependency: "google/protobuf/timestamp.proto"
-  message_type {
-    name: "Metric"
-    field {
-      name: "timestamp"
-      number: 1
-      label: LABEL_OPTIONAL
-      type: TYPE_MESSAGE
-      type_name: ".google.protobuf.Timestamp"
-      json_name: "timestamp"
-    }
-    field {
-      name: "id"
-      number: 2
-      label: LABEL_OPTIONAL
-      type: TYPE_STRING
-      json_name: "id"
-    }
-    field {
-      name: "data"
-      number: 3
-      label: LABEL_OPTIONAL
-      type: TYPE_MESSAGE
-      type_name: ".google.protobuf.Any"
-      json_name: "data"
-    }
-  }
-  options {
-    go_package: "github.com/containerd/containerd/api/types;types"
-  }
-  syntax: "proto3"
-}
 file {
   name: "github.com/containerd/containerd/api/services/tasks/v1/tasks.proto"
   package: "containerd.services.tasks.v1"