* win_scheduled_task: Added frequency: once and check_mode support
This patch includes:
- Renamed `execute:` parameter to `executable:`
- Renamed `argument:` parameter to `arguments:`
- Implemented `frequency: once` support
- Implemented check_mode support
- Fix idempotency issue related to empty description
- Added integration tests
* Improve the integration test structure
I think this is a great way to test normal mode and check-mode from the same playbook.
* Small fixes after review
