Default to SAF if available

[CaptainBeyondDS8]

I think if SAF is available then it should be the default. I think this is also about when SD cards become read only (without SAF) by default, so the built-in file selector is useless unless the system is patched to allow RW access to the card.

I'm almost inclined to just throw away the built-in selector, force SAF, and raise the target SDK version.

[CaptainBeyondDS8]

It occurred to me that we still need the built-in file selector to be able to edit files as root.

Perhaps we could make it a separate option, or long-pressing "open file" could still pull up the built-in selector.