Refactor integration tests to use stateful fakes and fixtures

[allenporter]

Motivation

Following the merge of the roborock.testing library (#860), this PR refactors integration tests in test_device_manager.py to use FakeRoborockCloud and V1VacuumSimulator. In doing so, we introduce some usability improvements to roborock.testing to simplify test implementation for both internal and downstream consumers (like the Home Assistant integration):

1. Eliminated Nested Patcher Contexts: Refactored patch_device_manager to be exposed as a standard pytest fixture. This removes the need for deep with cloud.patch_device_manager(): indentation, especially when asserting reconnection backoffs in background tasks which must run across the entire lifespan of the test.
2. Simplified Transport-Level Error Injection: Added a first-class inject_error(exception) and clear_error() API to FakeChannel. Test writers can now easily simulate and recover from connection/subscription/publish failures without hacky manual modification of mock side_effect attributes and private wrappers.
3. Type-Safe EAPI Response Mocking: Modified set_homes_response() on FakeWebApiClient to accept the HomeData dataclass directly (serializing it automatically under the hood). Added a get_default_home_data() helper so tests can retrieve the default registered layout and copy/modify it using standard dataclasses.replace rather than building raw dictionaries from scratch.
4. Unified Callback Interception: Refactored the simulator's RPC routing to use a first-class publish_handler registration property on FakeChannel instead of overriding mock attributes directly, keeping the mock assertions clean and orthogonal.
5. Self-Contained Sleep Mocking: Added reconnection sleep backoff patching directly inside patch_device_manager()'s context manager. Downstream integration test suites run instantly out-of-box without needing duplicate sleep-patching fixtures.

Changes Made

• roborock.testing:
  • channel.py: Added publish_handler, inject_error(exception), clear_error(), and _default_publish_handler(message).
  • cloud.py: Added get_default_home_data() and refactored set_homes_response(home_data). Patched MIN_BACKOFF_INTERVAL and MAX_BACKOFF_INTERVAL inside patch_device_manager().
  • simulator.py: Refactored simulator routing to register on publish_handler instead of mutating mock objects.
• tests:
  • conftest.py: Created shared fixtures cloud, fake_device, and patch_device_manager to be globally accessible.
  • test_device_manager.py: Completely refactored integration tests to use stateful fakes, fixtures, error injection, and dataclass-based home details response overrides.