refact(target): Switch subtype attributes to oneof

This updates the target resources to use a oneof for attributes. This
allows requests to the targets service to leverage the new
subtypes.AttributeTransformerInterceptor so that attributes are strongly
typed prior to the service handler.

internal/tests/api/targets/target_test.go

@@ -169,7 +169,13 @@ func TestList(t *testing.T) {
 	assert.ElementsMatch(comparableSlice(expected[:1]), comparableSlice(ul.Items))
 
 	for i := 1; i < 10; i++ {
-		tcr, err = tarClient.Create(tc.Context(), "tcp", proj.GetPublicId(), targets.WithName(expected[i].Name))
+		tcr, err = tarClient.Create(
+			tc.Context(),
+			"tcp",
+			proj.GetPublicId(),
+			targets.WithName(expected[i].Name),
+			targets.WithTcpTargetDefaultPort(uint32(i)),
+		)
 		require.NoError(err)
 		expected[i] = tcr.Item
 	}
@@ -183,6 +189,13 @@ func TestList(t *testing.T) {
 	require.NoError(err)
 	assert.Len(ul.Items, 1)
 	assert.Equal(filterItem.Id, ul.Items[0].Id)
+
+	filterstr := fmt.Sprintf(`"/item/attributes/default_port"==%d`, uint32(filterItem.Attributes["default_port"].(float64)))
+	ul, err = tarClient.List(tc.Context(), proj.GetPublicId(),
+		targets.WithFilter(filterstr))
+	require.NoError(err)
+	assert.Len(ul.Items, 1)
+	assert.Equal(filterItem.Id, ul.Items[0].Id)
 }
 
 func comparableSlice(in []*targets.Target) []targets.Target {