Use --single-process for faster Chrome automation

I'm seeing about a 30% speed improvement with this set

On my machine:
- running runAll with priority 1
- with only the first 25 tests in the desktop config
- averaged across 5 runs
- average run time without --single-process: 563 seconds
- average run time with --single-process: 386 seconds

See: https://github.com/GoogleChrome/chrome-launcher/blob/main/docs/chrome-flags-for-tools.md

config/configCommon.js

@@ -7,7 +7,8 @@ module.exports = {
 	engineOptions: {
 		headless: 'new',
 		args: [
-			'--no-sandbox'
+			'--no-sandbox',
+			'--single-process'
 		]
 	},
 	debug: false,