[Internal] Add unit tests for iam users/groups/spns lists and remove them from integration test

[tanmay-db]

What changes are proposed in this pull request?

The iam list integration tests just make the list calls for users/groups/spns and compare it with make the call through SDK. This is not ideal because the number of users / groups / spns can change since test run in parallel across multiple SDKs, PR leading to this test being flaky and blocking PRs to merge (need to run the test again and again for it to pass since it's flaky).

We should still test the pathway so it's covered with unit tests.

How is this tested?

Unit tests

[github-actions[bot]]

If integration tests don't run automatically, an authorized user can run them manually by following the instructions below:

Trigger: go/deco-tests-run/sdk-py

Inputs:

• PR number: 837
• Commit SHA: f61c48ebd79b93f0533f05e88bcd751612ddc3a6

Checks will be approved automatically on success.

[eng-dev-ecosystem-bot]

Test Details: go/deco-tests/12297821534