Several changes for using MediaStore

- Change config key name so default downloads to folder 'Download'
- Always use getFile as we do not need existing file deleted
- Fallback to use File based I/O pre API 29 as officially MediaStore
  APIs do not support general purpose usage. And also, it was working
  fine on all devices before. If it ain't broke, don't fix it
- Show full download path in settings to make it more clear to the user
- Close streams after using them

app/src/main/java/com/topjohnwu/magisk/ktx/XJava.kt

@@ -21,7 +21,8 @@ fun ZipInputStream.forEach(callback: (ZipEntry) -> Unit) {
     }
 }
 
-fun InputStream.writeTo(file: File) = this.copyTo(file.outputStream())
+fun InputStream.writeTo(file: File) =
+    withStreams(this, file.outputStream()) { reader, writer -> reader.copyTo(writer) }
 
 inline fun <In : InputStream, Out : OutputStream> withStreams(
     inStream: In,