Add GSM & Berglas Terraform modules to other infrastructure projects

Created by: ElizabethStirling

We need to enable / configure GSM for any projects in our infrastructure repository which need to use secrets.

Subdirectories: dotcom dogfood fair.io buildkite cmd site 24x7 gcp dns code-intel docker-images [anything with a company name]

Dependencies: #17806 (closed), #17807 (closed)

Useful Links: Example Terraform module Using Terraform modules

Repository: Infrastructure