Importers are written to convert third-party collection formats to a
Windows OBS scene collection. The Studio importer is capable of
translating scene collections to the correct types for the current
operating system. This change makes it so all imports will be ran
through the Studio translation, not just Studio and SL collections.
This replaces the previous Open File dialog for importing collections
with a window for importing many collections at once, based on the remux
window, along with support for importing from OBS Classic, XSplit
Broadcaster and from Streamlabs' fork. This also translates sources
between OSes that Studio supports.