Use explicit file protocol for AVIO

AVIO expects a `url` to locate a resource.

Use the file protocol to handle filenames containing colons.

Fixes #5487 <https://github.com/Genymobile/scrcpy/issues/5487>
PR #5499 <https://github.com/Genymobile/scrcpy/pull/5499>
Signed-off-by: Romain Vimont <rom@rom1v.com>