[terraform] add terraform apply to aws-deploy script

Summary:
This adds terraform apply to the aws-deploy script so the user doesn't have to
run it themselves manually

Depends on D12960

Test Plan:
ran the script on an aws account with empty deployments. Initialized the new keyserver.
One second running of the script, ran through the migration process

Reviewers: bartek, varun

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13045