This now relies on the implementation to set these flags on short reads/writes
instead of the higher level checking if SDL_SetError() was called.
Additionally (and crucially), this now sets ERROR or EOF on all short reads,
across all backends, not just when we get a zero-byte return value.
Fixes#13720.
This still logs backend choices, but we might use it for other things. For
example, what Android device is being used, or all the devices we enumerated,
etc.
Ideally this eventually logs all the stuff we often have to ask followup
questions about.
