[PP-1] Add form--extrasmall class to forms with operations dropbutton

Postponed on #3083256: Create smaller variations for form elements

Problem/Motivation

Claro automatically sets operations dropbuttons to '#type' => 'extrasmall'. If the operations dropbutton is accompanied by other form elements, those form elements will still be at their default size, and the form elements will not have inconsistent sizes.

When #3083256: Create smaller variations for form elements is added to core, the form--small and form--extrasmall classes will be made available. Wrapping a form in these classes will results in all form elements taking on their small/extrasmall variants, and eliminate the issue of inconsistent sizes.

Steps to reproduce

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Proposed resolution

Find the best way to wrap forms with operations dropbuttons in form--extrasmall.
If the method used is comprehensive enough, also remove the prerender enforcing the extrasmall variant for operations dropbuttons,

in ClaroPreRender

/**
   * Prerender callback for the Operations element.
   */
  public static function operations($element) {
    if (empty($element['#dropbutton_type'])) {
      $element['#dropbutton_type'] = 'extrasmall';
    }
    return $element;
  }

In claro.theme

// Add a pre-render function for Operations to set #dropbutton_type.
  if (isset($type['operations'])) {
    // In Claro, Operations should always use the extrasmall dropbutton variant.
    // To add CSS classes based on variants, the element must have the
    // #dropbutton_type property before it is processed by
    // \Drupal\Core\Render\Element\Dropbutton::preRenderDropbutton(). This
    // ensures #dropbutton_type is available to preRenderDropbutton().
    $operations_pre_renders = !empty($type['operations']['#pre_render']) ? $type['operations']['#pre_render'] : [];
    array_unshift($operations_pre_renders, [ClaroPreRender::class, 'operations']);

    $type['operations']['#pre_render'] = $operations_pre_renders;
  }

Remaining tasks

After implementing, address any @todo items referencing this issue.

User interface changes

API changes

Data model changes

Release notes snippet