picking video file: remove scoped storage api

[Funami580]

Not sure, if this is the direction this project wants to go, but I thought I’d give it a try. I added the permission to manage the entire storage, like VLC does: https://github.com/videolan/vlc-android/blob/2e6e0bd6a6667af607824ffbd5f11b746026f8a9/application/vlc-android/AndroidManifest.xml#L13. The logic is based on https://stackoverflow.com/a/78813970. Now we can select a video file without granting permissions each time. The problem of granting permissions was also described in #28:

Agree with this request, this app would be perfect if I don't need to grant file access to MpvKT everytime when I choose FilePicker (which requires users to click at least twice)

For now, this will probably take more clicks than before as one has to select the specific directory, but this can be alleviated in the future by adding options to open the last directory or bookmark directories.

[Pentaphon]

Not sure, if this is the direction this project wants to go, but I thought I’d give it a try. I added the permission to manage the entire storage, like VLC does

Based on the reaction to #185 I say that is where the community wants it to go since the current file picker solution is not good. I think everybody wants, at the minimum, a file manager like Next Player or at most, a library like VLC.

[abdallahmehiz]

I am working on a Solution using the MediaStore APIs but progress has been pretty slow cause life, I'll keep this PR open for now, might inspire some code from it.