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

* Moving plugins to use hashicorp go-plugin.

* Tweaks from feedback.

plugin/plugintest/hooks.go

@@ -7,7 +7,6 @@ package plugintest
 import http "net/http"
 import mock "github.com/stretchr/testify/mock"
 import model "github.com/mattermost/mattermost-server/model"
-import plugin "github.com/mattermost/mattermost-server/plugin"
 
 // Hooks is an autogenerated mock type for the Hooks type
 type Hooks struct {
@@ -39,6 +38,29 @@ func (_m *Hooks) ExecuteCommand(args *model.CommandArgs) (*model.CommandResponse
 	return r0, r1
 }
 
+// Implemented provides a mock function with given fields:
+func (_m *Hooks) Implemented() ([]string, error) {
+	ret := _m.Called()
+
+	var r0 []string
+	if rf, ok := ret.Get(0).(func() []string); ok {
+		r0 = rf()
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]string)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func() error); ok {
+		r1 = rf()
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // MessageHasBeenPosted provides a mock function with given fields: post
 func (_m *Hooks) MessageHasBeenPosted(post *model.Post) {
 	_m.Called(post)
@@ -95,13 +117,13 @@ func (_m *Hooks) MessageWillBeUpdated(newPost *model.Post, oldPost *model.Post)
 	return r0, r1
 }
 
-// OnActivate provides a mock function with given fields: _a0
-func (_m *Hooks) OnActivate(_a0 plugin.API) error {
-	ret := _m.Called(_a0)
+// OnActivate provides a mock function with given fields:
+func (_m *Hooks) OnActivate() error {
+	ret := _m.Called()
 
 	var r0 error
-	if rf, ok := ret.Get(0).(func(plugin.API) error); ok {
-		r0 = rf(_a0)
+	if rf, ok := ret.Get(0).(func() error); ok {
+		r0 = rf()
 	} else {
 		r0 = ret.Error(0)
 	}
@@ -137,7 +159,7 @@ func (_m *Hooks) OnDeactivate() error {
 	return r0
 }
 
-// ServeHTTP provides a mock function with given fields: _a0, _a1
-func (_m *Hooks) ServeHTTP(_a0 http.ResponseWriter, _a1 *http.Request) {
-	_m.Called(_a0, _a1)
+// ServeHTTP provides a mock function with given fields: w, r
+func (_m *Hooks) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	_m.Called(w, r)
 }