Default the Windows standalone app to ASIO

[sdatkinson]

Summary

• default newly created Windows standalone settings to ASIO instead of DirectSound
• preserve explicit driver values in existing settings.ini files
• keep plug-in targets and non-Windows standalone builds on their existing defaults

Dependency

• Allow apps to choose the default audio driver iPlug2#18 adds the app-configurable standalone driver default used here

Tests

• confirmed the focused preprocessing check failed before the change because no Windows standalone override existed
• confirmed Windows standalone preprocessing resolves APP_DEFAULT_AUDIO_DRIVER to 1 while Windows plug-in and non-Windows standalone configurations do not define an override
• built NeuralAmpModeler-app Release x64 with MSBuild
• git diff --check

The hardware-specific startup crash could not be reproduced locally without an affected DirectSound device configuration.

Resolves #655