scheduled_task : Refactor win32taskscheduler_spec

win32taskscheduler_spec is a legacy test file that we're keeping around to vet backward compatibility

• There are tests in there that are probably no longer necessary
• There are tests for both the taskscheduler_api2 provider and the win32_taskscheduler provider, but the file is named win32_taskscheduler_spec.rb - the file should be renamed to something like provider_spec.rb
• There is extensive / complicated mocking
• Some of the tests duplicate what's in other tests (like the task integration tests or the trigger unit tests)

Audit the tests, clean them up, rename the file, etc.