Make PageLayoutSource compatible with attributes

Problem/Motivation

As a follow-up of #3612556: PageLayoutSource is sometimes not rendered.

We can't apply styles to PageLayoutSource.

Proposed resolution

Proposal 1: let's assume some source plugins don't handle attributes

PageLayoutSource is not the only source returning a renderable not compatible with #attributes, do we:

• test the renderable on Display Builder side, and load the Style & Tokens panels only if compatible?
• add a specific plugin attributes on UI Patterns side, and load the Style & Tokens panels only if compatible?

If we do something like that, we also need to remove content (a leftover of an intermediary state of #3612556: PageLayoutSource is sometimes not rendered, may be harmful) here:

$build['content'][$slot_id] = $slot;

Proposal 2: Make PageLayoutSource compatible with attributes

For example, by wrapping the page renderable:

    return [
      // `page` renderable doesn't accept #attributes, so let's wrap it up to
      // be able to apply styles and other dynamic attributes.
      '#type' => 'html_tag',
      '#tag' => 'div',
      'content' => $page,
    ];

However, this is not working with every themes:

• UI suite DaisyUI: ✅ good layout rendering and styles correctly applied
• UI suite Material: ✅ good layout rendering and styles correctly applied
• UI suite DSFR: ✅ good layout rendering and styles correctly applied
• UI suite Bootstrap: ❌ page renderable is not rendered
• UI suite USWDS: ❌ page renderable is not rendered
• bootstrap with I suite Bootstrap styles: ✅ good layout rendering and styles correctly applied