E2E: Add GutenbergCoreE2E TC project - #86949

@Automattic/team-calypso-platform, I wanted to add a TC project to start running the core E2E tests. This is still in a PoC stage because we need to identify the specs we cannot run due to the environmental discrepancies. Also, the current way we're setting it up might be better in terms of maintenance. At this point, there is no built-in way to override the necessary login and rest E2E utilities, so we need to patch them. It's not a big patch, but it's still a patch rather than a project config.

Regarding the project file itself, since we cannot test it from a branch, I really need some eyes on it. I've never added a project to TC, so I'm not sure if I'm doing anything right here. 🙏

cc: @kevin940726

Thanks for working on this! ❤️

Since pretty much we're only adding new artifacts, and as long as IntelliJ is not complaining about compilation errors, merging to test it out should be safe. We can always revert if things go awry. Unfortunately, there's no better way to test, but we already accepted that workflow of merging/reverting as needed for TeamCity.

Regarding the code, it looks good. I'm fine creating a new project for it, but I'm wondering if, since this will be a dotcom-related test, if we should just add the new build under the existing WPCom_Tests project instead?

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

Thank you again for your work here, Bart! ❤️

I'll try to get it before the EOW to get the build on TC and start experimenting with it!

EDIT: Didn't get to it this week, but will do so the next one.