AiVdbProviderClientBase depends on classes in the ai_search submodule

The idea is that AiVdbProviderInterface can be implemented in some other way than AI Search yet still be relied to actually make queries/searches e.g. for agent calls or other functionality so maybe we need something like this:

new src/Base/AiVdbProviderStandaloneClientBase.php:

abstract class AiVdbProviderStandaloneClientBase implements AiVdbProviderInterface, ContainerFactoryPluginInterface {
   ...
}

existing src/Base/AiVdbProviderClientBase.php:

if (interface_exists('\Drupal\ai_search\AiVdbProviderSearchApiInterface')) {
  abstract class AiVdbProviderClientBase extends AiVdbProviderStandaloneClientBase implements AiVdbProviderSearchApiInterface {
     ...
  }
}

... With an else on the latter in case ai search is disabled I guess

Why not just split out the Search API dependent code to the ai_search submodule, rather than conditional logic?

There also seems to be some entanglement with both:

• \Drupal\ai\AiVdbProviderInterface::querySearch() and
• \Drupal\ai\AiVdbProviderInterface::vectorSearch()

depending on the output of \Drupal\ai_search\AiVdbProviderSearchApiInterface::prepareFilters() in the ai_search submodule.

Should these be moved to the ai_search submodule too?

Created a MR that splits out this dependency.