fix: #3620423 Install metatag_views for the shipped views display extender

Issue: https://www.drupal.org/project/varbase_seo_base/issues/3620423

varbase_admin_base ships two views declaring metatag_display_extender:

• config/views.view.content.yml
• config/views.view.user_admin_people.yml

That plugin comes from the metatag_views submodule of drupal/metatag, and nothing in the chain installed it.

Why this recipe. It requires drupal/metatag: ~2 and already installs eight metatag submodules (metatag, eca_metatag, metatag_facebook, metatag_google_plus, metatag_hreflang, metatag_mobile, metatag_open_graph, metatag_twitter_cards, metatag_verification). varbase_admin_base does not require drupal/metatag at all, so it cannot own a metatag submodule even though it ships the config that needs it.

On Varbase the install profile enables the submodule and the gap is invisible. On a Drupal CMS base nothing does:

PluginNotFoundException: The "metatag_display_extender" plugin does not exist.
Valid plugin IDs for Drupal\views\Plugin\ViewsPluginManager are: default

Verified on Drupal CMS 2.x / core 11.4.5 with drupal/educare:1.0.x-dev: with the module installed, metatag_views is enabled and the exception is gone.

Ordering note for reviewers: this recipe applies later in a site-template chain than varbase_admin_base, which imports the views. That is fine — a display extender is only needed when a view is executed, not when its config is saved. If a later failure shows it is needed earlier, that is a separate ordering question, not a reason to move the dependency into a recipe that does not require metatag.

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