add: reencode album feature

for now presets which are featured in the GUI are: mp3, aac, opus, lossless.

to-refactor: AlbumReencoder.cpp, backend code is currently longer than needed! we can shorten it. with seperating the raii handlers into a seperate class

CMakeLists.txt

@@ -38,6 +38,7 @@ set(SOURCES
     src/engine/SpectrumAnalyzer.cpp
     src/engine/MusicLibrary.cpp
     src/engine/MetadataReader.cpp
+    src/engine/AlbumReencoder.cpp
     # ffmpeg
     src/engine/ffmpeg/FormatContext.cpp
     src/engine/ffmpeg/CodecContext.cpp
@@ -48,6 +49,8 @@ set(SOURCES
     src/playlists/PlaylistManager.cpp
     src/playlists/PlaylistCreatorDialog.cpp
     src/playlists/PlaylistBrowserDialog.cpp
+    # reencode
+    src/gui/ReencodeDialog.cpp
 )
 set(HEADERS
     src/config/Config.h
@@ -71,6 +74,8 @@ set(HEADERS
     src/engine/Track.h
     src/engine/MetadataReader.h
     src/engine/MusicLibrary.h
+    src/engine/ReencodeJob.h
+    src/engine/AlbumReencoder.h
     # ffmpeg wrapper
     src/engine/ffmpeg/FormatContext.h
     src/engine/ffmpeg/CodecContext.h
@@ -81,6 +86,8 @@ set(HEADERS
     src/playlists/PlaylistManager.h
     src/playlists/PlaylistCreatorDialog.h
     src/playlists/PlaylistBrowserDialog.h
+    # reencode
+    src/gui/ReencodeDialog.h
 )
 # qrc resources
 set(RESOURCES