Share logic for saving page/cover (#6787)

* Use MediaStore on newer Android Q or newer

* Use flow instead of Observable

* Review comment fixes

* Use suspended function instead of flow

app/src/main/java/eu/kanade/tachiyomi/AppModule.kt

@@ -7,6 +7,7 @@ import eu.kanade.tachiyomi.data.cache.CoverCache
 import eu.kanade.tachiyomi.data.database.DatabaseHelper
 import eu.kanade.tachiyomi.data.download.DownloadManager
 import eu.kanade.tachiyomi.data.preference.PreferencesHelper
+import eu.kanade.tachiyomi.data.saver.ImageSaver
 import eu.kanade.tachiyomi.data.track.TrackManager
 import eu.kanade.tachiyomi.data.track.job.DelayedTrackingStore
 import eu.kanade.tachiyomi.extension.ExtensionManager
@@ -46,6 +47,8 @@ class AppModule(val app: Application) : InjektModule {
 
         addSingletonFactory { DelayedTrackingStore(app) }
 
+        addSingletonFactory { ImageSaver(app) }
+
         // Asynchronously init expensive components for a faster cold start
         ContextCompat.getMainExecutor(app).execute {
             get<PreferencesHelper>()