tools: Migrate remaining tools to gobin

Replace ./scripts/install_tool.sh with `gobin`, such that we have
consistent handling for all tools needed for build and consistent
versioning within ./tools/mod/go.mod.

Side changes:
  - Expose /scripts/fix.sh that fixes formatting and bom across modules
  - Expose *.sh variants of scripts like build and ./test (first step
towards replacement).
  - Make stderr output of commands explicit and make commands use
different color than callouts.

tools/mod/libs.go

@@ -0,0 +1,25 @@
+// Copyright 2016 The etcd 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.
+
+// +build libs
+
+// This file implements that pattern:
+// https://github.com/golang/go/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module
+// for etcd. Thanks to this file 'go mod tidy' does not removes dependencies.
+
+package libs
+
+import (
+	_ "github.com/gogo/protobuf/proto"
+)