Layout Support: Replace incremental IDs with hashes

[DAreRodz]

What?

Changes how class names for layout containers are generated, replacing per-block, incrementally-generated IDs with hashes obtained from the layout styles definition.

Will fix #67308.

Why?

Since #67826, the Interactivity API's client-side navigation feature replaces all style sheets when navigate is called.

This currently affects the style of elements outside of router regions, even when navigating between pages generated with the same template, because layout class names depend on the number of blocks rendered using them (see #67826), which can vary.

How?

The PR adds a new function named gutenberg_unique_prefixed_id_from_array, which basically generates a short hash from the passed array.

This function is used to generate the layout container class, receiving all the data required to generate the style output. That guarantees hashes to be unique for each layout style combination.

Testing Instructions

TBD

Screenshots or screencast

Before	After
Screen.Recording.2024-12-20.at.13.45.58.mov	Screen.Recording.2024-12-20.at.13.48.13.mov

[github-actions]

Flaky tests detected in 9c568ad.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/12436771786
📝 Reported issues:

• [Flaky Test] Navigates the items list via UP/DOWN arrow keys #64334 in /test/e2e/specs/site-editor/dataviews-list-layout-keyboard.spec.js

[talldan]

Added some potential reviewers for when this is ready.