MM-10702 Moving plugins to use hashicorp go-plugin. (#8978)

* Moving plugins to use hashicorp go-plugin.

* Tweaks from feedback.

plugin/hclog_adapter.go

@@ -0,0 +1,73 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package plugin
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/hashicorp/go-hclog"
+	"github.com/mattermost/mattermost-server/mlog"
+)
+
+type HclogAdapter struct {
+	wrappedLogger *mlog.Logger
+	extrasKey     string
+}
+
+func (h *HclogAdapter) Trace(msg string, args ...interface{}) {
+	h.wrappedLogger.Debug(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+}
+
+func (h *HclogAdapter) Debug(msg string, args ...interface{}) {
+	h.wrappedLogger.Debug(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+}
+
+func (h *HclogAdapter) Info(msg string, args ...interface{}) {
+	h.wrappedLogger.Info(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+}
+
+func (h *HclogAdapter) Warn(msg string, args ...interface{}) {
+	h.wrappedLogger.Warn(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+}
+
+func (h *HclogAdapter) Error(msg string, args ...interface{}) {
+	h.wrappedLogger.Error(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+}
+
+func (h *HclogAdapter) IsTrace() bool {
+	return false
+}
+
+func (h *HclogAdapter) IsDebug() bool {
+	return true
+}
+
+func (h *HclogAdapter) IsInfo() bool {
+	return true
+}
+
+func (h *HclogAdapter) IsWarn() bool {
+	return true
+}
+
+func (h *HclogAdapter) IsError() bool {
+	return true
+}
+
+func (h *HclogAdapter) With(args ...interface{}) hclog.Logger {
+	return h
+}
+
+func (h *HclogAdapter) Named(name string) hclog.Logger {
+	return h
+}
+
+func (h *HclogAdapter) ResetNamed(name string) hclog.Logger {
+	return h
+}
+
+func (h *HclogAdapter) StandardLogger(opts *hclog.StandardLoggerOptions) *log.Logger {
+	return h.wrappedLogger.StdLog()
+}