Docker tests fail due to CSR dependency

[eeaton]

TL;DR

For new contributors, it is impossible to follow the guidance at contributing.md and run make docker_test_prepare due to a dependency on CSR, which is deprecated.

This issue is seen in #1304, and makes it much harder for a contributor to make a relatively simple PR contribution because they are unable to check CI tests themselves.

Expected behavior

docker tests to create resources and run tests against them should not depend on CSR, because the docker tests are not actually creating any version-controlled repos.

This should be available to any customer environment, regardless of whether they are grandfathered in to continue using CSR because they had enabled the API prior to deprecation.

Observed behavior

docker tests fail, because there are multiple places that try to enable sourcerepos.googleapis.com and then run tests checking that sourcerepos.googleapis.com must be enabled.

Terraform Configuration

See all instances where CSR is enabled or checked for in CI tests:
https://github.com/search?q=repo%3Aterraform-google-modules%2Fterraform-example-foundation+sourcerepo.googleapis.com&type=code

Terraform Version

same outcome with any Terraform version.

The determining factor whether this works or fails is whether the customer Organization had used CSR prior to [deprecation on June 17 2024](https://cloud.google.com/source-repositories/docs?), in which case they have a limited legacy exception to continue using CSR. All new customer orgs will fail.

Additional information

No response