Maintain source info in the database. (#6389)

* Maintain Source Info in database

* Review changes and cleanups

* Review changes 2

* Review Changes 3

(cherry picked from commit 9d5b7de1d8)

# Conflicts:
#	app/src/main/java/eu/kanade/domain/DomainModule.kt
#	app/src/main/java/eu/kanade/presentation/browse/MigrateSourceScreen.kt
#	app/src/main/java/eu/kanade/tachiyomi/extension/ExtensionManager.kt
#	app/src/main/java/eu/kanade/tachiyomi/source/SourceManager.kt

app/src/main/res/values/strings.xml

@@ -737,6 +737,7 @@
     <string name="migrate">Migrate</string>
     <string name="copy">Copy</string>
     <string name="empty_screen">Well, this is awkward</string>
+    <string name="not_installed">Not installed</string>
 
     <!-- Downloads activity and service -->
     <string name="download_queue_error">Couldn\'t download chapters. You can try again in the downloads section</string>