Try to fix extractFS when saves have nested dirs

[gregoo]

A stab at fixing "Failed to open file for writing". What seem to happen is that QFile::open is used on a non existing folder and such fails.

This adds an extra step ensuring that the whole path to the extracted file is created before opening it.

(Also I'm in no way a C++ developer and I have no clue what side effects it may have produced)

(Note: also discussed this here: https://github.com/eliboa/NxNandManager/issues/100#issuecomment-1343302780)