Switch Rucio server to SRC IAM for auth provision

The Rucio instance has been integrated with the ESCAPE IAM service historically. Since the SRC IAM service is now up and running and ESCAPE is drawing to a close, it would be good to migrate to using the SRC IAM in order to prevent accruing of further technical debt. If more storage sites are added to the datalake before this migration is done, we would be adding to the collective technical debt across the ART.

Update: This is becoming especially critical now we're working on APIs. At the moment the data-management IAM client is managed by the ESCAPE IAM instance as some endpoints require token exchanges against the Rucio "auth" client (which has always lived on the ESCAPE IAM instance) to do work within the Rucio ecosystem. As such, the data-management API cannot be integrated with any other API (e.g. permissions) with clients utilising the SKA IAM.

In PI23, a number of blockers for this work were identified, and then worked around. Chief among these was the inability to continue to use the CERN Pilot FTS for SRCNet 0.1. This meant that we had to switch to using the SRCNet FTS instance instead, initially with ESCAPE IAM tokens. Given that this only occurred in Sprint 5, we felt it sensible to allow some time for the functional tests to verify the reliability of this FTS instance, and give the RSE operators some advance warning of the impending switch to SKA IAM (some small config changes are required to the RSE storage resource managers to enable this)

Can be tested by authing with the rucio client. 

General status:

https://monit.srcdev.skao.int/grafana/public-dashboards/2846c870a07d48c68a046886918cbac6?orgId=1

Transfers following switchover (dotted line)