Extract four categories of copy-pasted test code into single
canonical locations:
- POLICY_OBJECT_TYPE / DRAFT_CHUNK_OBJECT_TYPE constants that were
defined identically in both persistence/sqlite.rs and
persistence/postgres.rs are now owned by persistence/mod.rs.
- test_server_state() was duplicated across grpc/provider.rs,
grpc/policy.rs, and grpc/sandbox.rs. A shared grpc::test_support
module in grpc/mod.rs now owns the single implementation; each
submodule imports it.
- The TestOpenShell stub (full OpenShell trait impl), install_rustls_provider(),
PkiBundle, generate_pki(), and start_test_server() were copied across
up to five openshell-server integration test files. A new
tests/common/mod.rs module owns them; each test file uses mod common.
- StubResponse, unique_socket_path(), and spawn_podman_stub() were
duplicated between openshell-driver-podman/src/driver.rs and
openshell-driver-podman/src/grpc.rs. A new src/test_utils.rs
(cfg(test)-gated) owns the shared helpers.
