Add cloud sql proxy to logan

Some post-deployment operations for the IAM platform require the use of the cloud_sql_proxy utility provided by gcloud, this utility should therefore be added to the logan-terraform image so that the same configuration can be used for running these post-deploy commands.

Related to work done for https://gitlab.developers.cam.ac.uk/uis/devops/iam/card-database/feedback/-/issues/592.