alsa: Improve *_list_streams functions

Avoids including useless streams in the list and optimizes GList construction.
oss: Improve *_list_streams functions and handling of device streams

Makes the functions compatible with the ALSA code. As streams in OSS are not dynamic elements, they are removed as soon as they are known to be useless.
Remove ability to have no active switch option and fix OSS to correctly handle such case