Migrate EZID Prd RDS to graviton

[jsjiang]

Migrate EZID Prd RDS to graviton in the week of Jan 12.

• Preferred: Thursday Jan 15, during maintenance window 5-6 am
• schedule downtime in Escalope to disable Nagios alerts

[jsjiang]

Locust load tests results on 12/17 with current Intel platform:

• requests per sec: 4.36
• 50%ile response time (ms): 1900
• 95%ile repose time (ms): 6400