Add layout attribute POC

[reeganviljoen]

closses #2173

What are you trying to accomplish?

As per #2173 this adds a layout attribute, the main difference is that this monkey patches rails's render_in instead of making use of an upstream addition, this is supposed to act as a POC to strat the discusion about how the api looks like and top start next steps to get this done

Anything you want to highlight for special attention from reviewers?

This is not to be merged in its current state but to start the discusion for the api's implementation in view component and rails and how to achieve this

[reeganviljoen]

@joelhawksley I haven't done anything in a while and this POC was easy enough to setup to get my feet wet again, please have a look when you can

[joelhawksley]

Marking as draft as this is not meant to be merged ❤️

[reeganviljoen]

thank you @joelhawksley
please feel free to add some feedback, before I submit a pull request to rails
cc @boardfish

[joelhawksley]

Thanks for documenting this issue, I'll add it as a TODO to v4.