Return weapon settings from payload lua files and save weapon settings to pylon data in miz file

[zhexu14]

This PR expands support for DCS weapon settings (e.g. fuze settings) by:

• Returns weapon settings, if present, in UnitType.loadout and UnitType.loadout_by_name. These settings are already loaded by UnitType.load_payloads but are stripped out by these functions, which previously only returned the pylon number and clsid.
• Sets weapons settings in FlyingUnit.load_pylon so that when passed in, weapons settings are stored in the miz file.
• Fixes a bug in test_smoke_required_modules where a miz file was not cleaned up after tests run.