#26630 wrap command callbacks to ensure exceptions bubble up in Maya

Because we use evalDeferred for stability on Linux, we've exposed a bug in Maya that causes any exceptions that are raised during the callback to get "stuck" and could potentially cause a crash. This works around the issue by wrapping the callback in a try/except clause and logging our own exception with the error and traceback info.
should we perhaps say "silently discarded" or something instead of "stuck"? Feels clearer. Stuck sounds like things could hang.