add support for test mode detection in modulename.js via index.html (#3631)

in some cases the modulename.js may need to detect running in test mode
(compliments pr #3630)

window.name is not set  web mode

add a new field to the index.html 
window.intest 
and use the server_function to replace the hard coded string like we do
for window.mmversion=#VERSION#
then change the two  test helpers to set the env variable
app.js detects and sets global.intest=true
server func replace with value of global.intest

then module can use   if(window.intest)

tests/electron/helpers/global-setup.js

@@ -11,6 +11,7 @@ exports.startApplication = async (configFilename, systemDate = null, electronPar
 	if (systemDate) {
 		process.env.MOCK_DATE = systemDate;
 	}
+	process.env.mmTestMode = "true";
 
 	global.electronApp = await electron.launch({ args: electronParams });