Improve ps4 addon message handling

[Pelsin]

• The save message should not randomly disappear anymore
• Error/save message now resets after a new file is uploaded
• Should now only be possible to select one file per input
• Removed tons of lint errors
• The code is now formatted the same as the rest of the code base, hence the big change.

There are more things to improve, but this moves us a step forward.

• Please someone else also verify the upload still works 🙏

[arntsonl]

Great clean-ups thank you, easy win for PS4!