All resource configs loaded for each individual resource config

Problem/Motivation

I recently upgraded jsonapi + jsonapi_extras from 1.7 -> 1.10 and rc1 -> rc5 respectively. Our frontend is now taking 10-15 seconds longer to fetch each set of 50 nodes it is requesting. I profiled the request using xhprof and with the help of Gabriel, was able to identify that ConfigurableResourceTypeRepository::getResourceConfigs was invoked 500+ times for the single request, thus invoking EntityStorageBase::loadMultiple 500+ times:

    $resource_configs = $this->entityTypeManager
      ->getStorage('jsonapi_resource_config')
      ->loadMultiple($resource_config_ids);

Proposed resolution

Store $resource_configs in a property on the class or in cache so that subsequent calls do not need to load all resource configs again. Will post a patch shortly.

I believe this was introduced in #2941095: ResourceTypeRepository loads all configuration for every ->get($entity_type_id, $bundle).