Fix integration tests for databricks_entitlements

[mgyucht]

Changes

The integration tests for databricks_entitlements are now failing. I believe this is caused by a race condition between databricks_group and databricks_entitlements resources. In practice, these resources should not be used at the same time; instead, you should the former when you need to define the group in TF and the latter if the group is defined externally to TF.

First, I've improved the test coverage for entitlements to cover all resource types (user, group, service principal). As part of this, I've rewritten the tests to manage the resources externally from Terraform's perspective, so there are no more race conditions. Because of this, I'm able to remove the other integration tests, including the flaky one.

Tests

• make test run locally
• relevant change in docs/ folder
• covered with integration tests in internal/acceptance
• relevant acceptance tests are passing
• using Go SDK

[tanmay-db]

Went through the changes, LGTM.