internal/outcome: populate instance metadata for PipeWire

These have similar semantics to equivalent Wayland security-context-v1 fields.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/outcome/sppipewire_test.go

@@ -30,7 +30,9 @@ func TestSpPipeWireOp(t *testing.T) {
 			Ephemeral(system.Process, m(wantInstancePrefix), 0711).
 			// toSystem
 			PipeWire(
-				m(wantInstancePrefix + "/pipewire"),
+				m(wantInstancePrefix+"/pipewire"),
+				"org.chromium.Chromium",
+				"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
 			), sysUsesInstance(nil), nil, insertsOps(afterSpRuntimeOp(nil)), []stub.Call{
 			// this op configures the container state and does not make calls during toContainer
 		}, &container.Params{