Resolve Injekt dependencies directly from the Metro graph (#3965)

The previous setup had a circular dependency between Injekt
registration and extension loading.

In regard to #3931, I've moved the culprit ExtensionManager out of
Injekt altogether, alongside CoverCache, PreferenceStore and
TrackPreferences, none of which a source needs.

app/src/main/java/eu/kanade/domain/manga/model/Manga.kt

@@ -72,7 +72,7 @@ fun Manga.copyFrom(other: SManga): Manga {
     )
 }
 
-fun Manga.hasCustomCover(coverCache: CoverCache = Injekt.get()): Boolean {
+fun Manga.hasCustomCover(coverCache: CoverCache = Injekt.get<Context>().appGraph.coverCache): Boolean {
     return coverCache.getCustomCoverFile(id).exists()
 }