Switch from containers/image to go-containerregistry (#140)

* Vendor changes for go-containerregistry switch.

* Manual changes for go-containerregistry switch.

The biggest change is refactoring the tarball unpacking.

* Pull more of container-diff out.

* More vendor removals.

* More unit tests.

vendor/github.com/prometheus/common/model/model.go

@@ -1,16 +0,0 @@
-// Copyright 2013 The Prometheus 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 model contains common data structures that are shared across
-// Prometheus components and libraries.
-package model