Products megamenu as a data-driven catalog with a Solr product type-ahead

- evo_megamenu_json stays project-neutral: new panel layout "catalog";
  for such entries the MenuBuilder dispatches the new PSR-14 event
  BuildCatalogEvent and emits whatever a listener sets as `catalog`
  (null without a listener). The entry's teaser cards serve as the
  featured tiles; the teaser inline field now also shows for "catalog",
  and the entry form reloads when the layout changes. README section
  "Layout catalog"
- VITEC listener ProvideProductCatalog fills it, modelled on the Ross
  Video products menu: main categories below the "Product" root, their
  subcategories as groups, products with a plain-text one-line teaser;
  same visibility rules as the product list, Product Finder links
  (/products?cat=&subcat=), empty categories and groups left out, three
  queries for the whole catalog
- Product type-ahead GET /_json/?type=7385&q= (USER_INT page type,
  ProductMenuSearchJsonRenderer): Solr restricted to products, last term
  completed as a prefix, up to six product cards plus their titles as
  autocomplete suggestions; endpoint announced in catalog.search
- Spec v1.23 (clause 7.16: product type-ahead)

packages/evo_megamenu_json/Resources/Private/Language/locallang_db.xlf

@@ -24,6 +24,7 @@
       <trans-unit id="tx_evomegamenujson_entry.layout.description"><source>Columns for a structure menu, teaser cards for editorial sections such as news or stories.</source></trans-unit>
       <trans-unit id="tx_evomegamenujson_entry.layout.columns"><source>Columns</source></trans-unit>
       <trans-unit id="tx_evomegamenujson_entry.layout.teasers"><source>Link column plus teaser cards</source></trans-unit>
+      <trans-unit id="tx_evomegamenujson_entry.layout.catalog"><source>Catalog (data-driven: categories and items from the site package, teaser cards as featured tiles)</source></trans-unit>
       <trans-unit id="tx_evomegamenujson_entry.menu_columns"><source>Columns</source></trans-unit>
       <trans-unit id="tx_evomegamenujson_entry.menu_columns.description"><source>One column per group. In the teaser layout only the first column is rendered, next to the cards.</source></trans-unit>
       <trans-unit id="tx_evomegamenujson_entry.menu_teasers"><source>Teaser cards</source></trans-unit>