Add *testing.T field to TestCluster struct and initialize it in
startMiniCluster. This allows Stop() to properly log warnings when
cluster shutdown times out. Includes the t field in the test cluster
initialization and restores the logging statement in Stop().
- Create setup.go with TestCluster and S3TablesClient definitions
- Create client.go with HTTP client methods for all operations
- Test utilities and client methods organized for reusability
- Foundation for S3 Tables integration tests