webapp: install read-only services on all frontend servers

• move the storage and search installation in an upper level in the webapp classe tree because all the webapps will now have the same components installed
• Remove the useless swh_rp_webapp_with_swh_search_and_storage classe
• configure the webapp to use the local search and storage services
• fix an issue on the storage configuration on webapp1 that was not using the r/o credentials to access the database

Related to T3408