docker: Use swh-search with memory backend as default search engine

In order to have a search behavior close to the production one, add services
related to archive search in the default docker-compose.yml file:

• swh-search: remote search service using a memory backend
• swh-search-journal-client-objects: journal client feeding swh-search with objects loaded into the archive (typically origins)
• swh-search-journal-client-indexed: journal client feeding swh-search with results of swh-indexer processing on archived objects

As a consequence, it simplifies the docker-compose.search.yml file enabling
to use a swh-search service with a more costly elasticsearch backend.