Move Solr to dedicated servers in cloud mode

EPIC: #512

Description

Currently Solr runs on dolos in "core" mode (single-node) and takes disk space (~150Gb). The disk is ~80% full. See DBnomics dashboard

Move it to dedicated servers in cloud mode to:

• reduce disk usage of dolos
• load balance Solr queries
• improve resilience of Solr service
• modularize DBnomics architecture

Tasks

• provision 3 servers (or 2?)
• install Solr in cloud mode (preferably with Docker?)
• test indexing some providers, and make queries
• migrate existing index, or reindex all providers