Implement stable metric validation and verification

Based on KEP:
https://github.com/kubernetes/enhancements/blob/master/keps/sig-instrumentation/20190605-metrics-validation-and-verification.md

Add //test/instrumentation:stable_metric_test that compares metrics
in source code to those available in
"test/instrumentation/testdata/stable-metrics-list.yaml".

test/instrumentation/error.go

@@ -0,0 +1,59 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+)
+
+const (
+	errNotDirectCall        = "Opts for STABLE metric was not directly passed to new metric function"
+	errPositionalArguments  = "Positional arguments are not supported"
+	errStabilityLevel       = "StabilityLevel should be passed STABLE, ALPHA or removed"
+	errStableSummary        = "Stable summary metric is not supported"
+	errInvalidNewMetricCall = "Invalid new metric call, please ensure code compiles"
+	errNonStringAttribute   = "Non string attribute it not supported"
+	errFieldNotSupported    = "Field %s is not supported"
+	errBuckets              = "Buckets were not set to list of floats"
+	errLabels               = "Labels were not set to list of strings"
+	errImport               = `Importing through "." metrics framework is not supported`
+)
+
+type decodeError struct {
+	msg string
+	pos token.Pos
+}
+
+func newDecodeErrorf(node ast.Node, format string, a ...interface{}) *decodeError {
+	return &decodeError{
+		msg: fmt.Sprintf(format, a...),
+		pos: node.Pos(),
+	}
+}
+
+var _ error = (*decodeError)(nil)
+
+func (e decodeError) Error() string {
+	return e.msg
+}
+
+func (e decodeError) errorWithFileInformation(fileset *token.FileSet) error {
+	position := fileset.Position(e.pos)
+	return fmt.Errorf("%s:%d:%d: %s", position.Filename, position.Line, position.Column, e.msg)
+}