Migrate to pysolr to search with SOLR Cloud

THIS PR SHOULD NOT BE MERGED UNTIL WE HAVE ACCESS TO SOLR CLOUD FROM WP-K8S CLUSTER

With the migration to the SOLR Cloud the search wrapper needs to be updated to connect to SOLR Cloud. The pysolr is python library to connect to SOLR Cloud. This PR is to use SOLR Cloud instead of SOLR instance.

JIRA : https://www.ebi.ac.uk/panda/jira/browse/ENSWBSITES-1194

Currently, we have SOLR Cloud running at HL only on VMs.

In order to integrate the changes here, it needs the following.

1. Access to SOLR Cloud from WP-k8s cluster ENSWBSITES-1417
2. SOLR Cloud instances at both HX & HL ENSWBSITES-1416