chore: Per-module isolation for integration tests

[martijnvans]

An illustration of how per-module isolation will look in use. Ignore everything except test/setup/*.tf, as everything else is really just https://github.com/GoogleCloudPlatform/terraform-google-cloud-run/pull/404, but I didn't know how to base this PR on top of that one, sorry.

This PR cannot be merged without https://github.com/GoogleCloudPlatform/cloud-foundation-toolkit/pull/3201 being merged and released, and the version number bumped in this PR.