Remove dependency on core/drupal.ajax from contextual module

Problem/Motivation

Reduce the weight of the contextual JS, since it's used on most pages when user has access to it.

Steps to reproduce

Proposed resolution

change the jquery ajax call with this, seems to be enough

      // Perform an AJAX request to let the server render the contextual links
      // for each of the placeholders.
      if (uncachedIDs.length > 0) {
        const data = new URLSearchParams();
        uncachedIDs.forEach((id) => data.append('ids[]', id));
        uncachedTokens.forEach((id) => data.append('tokens[]', id));

        const req = new Request(Drupal.url('contextual/render'), {
          method: 'POST',
          body: data,
        });

        fetch(req)
          .then((res) => res.json())
          .then((json) =>
            Object.entries(json).forEach(([contextualID, html]) => {
              // Store the metadata.
              storage.setItem(`Drupal.contextual.${contextualID}`, html);
              // If the rendered contextual links are empty, then the current
              // user does not have permission to access the associated links:
              // don't render anything.
              if (html.length > 0) {
                // Update the placeholders to contain its rendered contextual
                // links. Usually there will only be one placeholder, but it's
                // possible for multiple identical placeholders exist on the
                // page (probably because the same content appears more than
                // once).
                $placeholders = $context.find(
                  `[data-contextual-id="${contextualID}"]`,
                );

                // Initialize the contextual links.
                for (let i = 0; i < $placeholders.length; i++) {
                  initContextual($placeholders.eq(i), html);
                }
              }
            }),
          )
          .catch((error) => console.warn(error));
      }

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet