Robustness: Handle stale COM objects and RPC server unavailability

[amirf147]

This PR addresses issues where pyvda becomes unresponsive after a Windows Explorer restart or other events that cause the Virtual Desktop COM objects to become stale.

Problem

When Explorer restarts, the underlying COM interfaces for virtual desktops are destroyed and re-created. Any existing pointers held by pyvda become invalid, leading to RPC_S_SERVER_UNAVAILABLE or RPC_E_DISCONNECTED errors.

Solution

• Retry Mechanism: Enhanced the _com_retry decorator to attempt the failed operation up to 3 times with an exponential backoff.
• Automatic Refresh: Upon encountering an RPC error, pyvda now automatically re-initializes its global managers instance, re-acquiring fresh COM pointers.
• Error Handling: Fixed a bug where RPC errors were incorrectly caught and re-raised as NotImplementedError in _get_object, preventing the retry logic from triggering.
• Log Cleanup: Downgraded benign RPC_E_CHANGED_MODE warnings (often triggered when multiple libraries try to initialize COM on the same thread with different modes) to debug logs to reduce noise during recovery.

Error Example

_ctypes.COMError: (-2147023174, 'The RPC server is unavailable.', (None, None, None, 0, None))

Steps to Reproduce

1. Have the latest version of Caster running.
2. Restart Windows Explorer (e.g., via Task Manager or by running taskkill /f /im explorer.exe && start explorer.exe in a terminal).
3. Attempt to switch to a specific workspace (e.g., "go work one") using the Caster command.
4. This calls the following function from castervoice\lib\windows_virtual_desktops.py:

def go_to_desktop_number(n):
    # Helps make sure that the target desktop gets focus
    windll.user32.AllowSetForegroundWindow(ASFW_ANY)
    VirtualDesktop(n).go()

5. Observe the _ctypes.COMError: (-2147023174, 'The RPC server is unavailable.') because the VirtualDesktop COM object has gone stale following the Explorer restart.