Adding EnsureBot plugin helper. (#10542)

* Adding EnsureBot plugin helper.

* Removing unessisary GetBot call.

* Moving to own file and error handling cleanup.

* Removing patch functionaliy. Plugins should manage their own bot account updates for now.

* Adding tests and cleaning up errors.

* Modify to not shadow err.

* Moving helpers to seperate interface.

* Feedback fixes

plugin/plugintest/example_hello_user_test.go

@@ -42,8 +42,11 @@ func Example() {
 	api.On("GetUser", user.Id).Return(user, nil)
 	defer api.AssertExpectations(t)
 
+	helpers := &plugintest.Helpers{}
+	defer helpers.AssertExpectations(t)
+
 	p := &HelloUserPlugin{}
-	p.SetAPI(api)
+	p.SetAPI(api, helpers)
 
 	w := httptest.NewRecorder()
 	r := httptest.NewRequest("GET", "/", nil)