Revamped InteractiveLayout based on grid module

[frederickobrien]

Part of the grid module cinematic universe (see #15428 for context), this updates InteractiveLayout to use the grid module, and adjusts layout routing to send older pieces to the older setup.

This is near identical to the implementation for StandardLayout save for one key difference. Here the article body itself uses the same grid system. This is to allow for Ed Design in particular to create bespoke article layouts easily. I wonder if this is actually preferable even for non-interactive articles? We could snap elements to the grid rather than using hardcoded negative margins.

The PR also does away with the legacy content__main-column--interactive class on the article body, which had lingered longer than it probably should.

Why

• This makes the starting point for interactive articles normality, rather than a layout which more often than not needs to be rearranged by the atom itself. This will directly lead to less hacky boilerplate DOM manipulation code in interactive atoms, which I think everyone is in favour of
• Aligns interactive articles with the Source design system and even opens the door to being merged with StandardLayout (if there's appetite for that)
• Like StandardLayout this will make it much easier to add new header/furniture arrangements as first class citizens of the platforms

Switchover

Discussion around how to handle older interactive articles is ongoing. This initial approach creates a InteractiveLayoutDeprecated template for pre-switchover date (TBD) articles to be sent through.

Some open questions:

• Do we want the most read sidebar to return?
• Possible to toggle whether ads appear in the article body specifically?
• Could/should/do we want to make InteractiveLayout and StandardLayout one and the same?
• How do we set and hold a contract around data attributes, etc.

Screenshots

Before	After

[github-actions]

Deploy build 27198 of dotcom:rendering-all to CODE

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From guardian/actions-riff-raff.

[frederickobrien]

Why this legacy class was still being applied: #3113

[github-actions]

Deploy build 1512 of dotcom:ab-testing to CODE

All deployment options

• Deploy build 1512 of dotcom:ab-testing to CODE
• Deploy parts of build 1512 to CODE by previewing it first
• What's on CODE right now?

---

From guardian/actions-riff-raff.