Add the separate utility class PlayButtonHelper to handle the initialization of the listeners.
The ClickListeners on playlist controls had different behaviours. This commit fixes that.
The commit also refactors the way how the app determines whether it is started for the first time. The previous version was not clean and recent in this PR caused it to fail.
* restore permission request popup previously removed in #2486
* use legacy file picker in cases where saf file picker is not available
* fix missing file check logic in prepareSelectedDownload method (DownloadDialog.java)
* use Java I/O (classic way) on older android versions
* use Storage Access Framework on newer android versions (Android Lollipop or later)
* both changes have the external SD Card write permission
* add option to ask the save path on each download
* warn the user if the save paths are not defined, this only happens on the first NewPipe run (Android Lollipop or later)
* re-work finished mission database
* re-work DownloadMission and bump it Serializable version
* keep the classic Java IO API
* SAF Tree API support on Android Lollipop or higher
* add wrapper for SAF stream opening
* implement Closeable in SharpStream to replace the dispose() method
* do required changes for this API:
** remove any file creation logic from DownloadInitializer
** make PostProcessing Serializable and reduce the number of iterations
** update all strings.xml files
** storage helpers: StoredDirectoryHelper & StoredFileHelper
** best effort to handle any kind of SAF errors/exceptions