Can we make SnapshotTesting compatible with background threads?

[tahirmt]

I don't know if it is possible but if someone is doing an image snapshot then yes it has to be on the MainActor but if someone wants to do a textual capture of url requests for example, I feel that shouldn't be required to run on the MainActor. Right now this line fails saying test observer can only be added or removed on the main thread which is also weird because it's already using a different queue. For context I'm using this with Quick/Nimble which changed everything to async with their last release so all tests run on the cooperative queue now unless moved to MainActor