[terraform] Introduce secondary keyserver service

Summary:
This introduces the secondary keyserver service. The task is mostly identical to the primary except COMM_NODE_ROLE being set to
secondary.

Depends on D12710

Test Plan:
I added a temporary keyserver route that printed true/false for whether it was primary. Load balancer properly distributed traffic
to both primary and secondary requests and was able to curl https://wyilio.com/role to get both true and false responses

Reviewers: varun, bartek

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12711