Improvements for next version of Cloud Run App module

As part of the work on the next version of the Cloud Run app module (gcp-cloud-run-app#47 (closed)) we need to make some changes to this module.

1. Tweak project definitions to allow the project to be specified via a variable or via the current google provider as a fallback.
2. This module doesn't contain any outputs making it impossible to test with the new terraform test command. This issue is to add some relevant outputs.
3. Remove maximum version constraints in line with Terraform best practices for reusable modules (see https://developer.hashicorp.com/terraform/language/expressions/version-constraints#terraform-core-and-provider-versions).
4. Also, while we're at it we should implement release automation seeing as that is working well in the gcp-secrets repo.