Add UnmeteredSource interface

To be included in extension-lib 1.3 (or whatever it's going to be). This applies to sources like Komga or Lanragi, where large numbers of update/download aren't of concern since they're (usually) self-hosted.

app/src/main/java/eu/kanade/tachiyomi/data/library/LibraryUpdateService.kt

@@ -25,6 +25,7 @@ import eu.kanade.tachiyomi.data.track.EnhancedTrackService
 import eu.kanade.tachiyomi.data.track.TrackManager
 import eu.kanade.tachiyomi.data.track.TrackService
 import eu.kanade.tachiyomi.source.SourceManager
+import eu.kanade.tachiyomi.source.UnmeteredSource
 import eu.kanade.tachiyomi.source.model.SManga
 import eu.kanade.tachiyomi.source.model.toSChapter
 import eu.kanade.tachiyomi.source.model.toSManga
@@ -267,7 +268,10 @@ class LibraryUpdateService(
             .sortedWith(rankingScheme[selectedScheme])
 
         // Warn when excessively checking a single source
-        val maxUpdatesFromSource = mangaToUpdate.groupBy { it.source }.maxOfOrNull { it.value.size } ?: 0
+        val maxUpdatesFromSource = mangaToUpdate
+            .groupBy { it.source }
+            .filterKeys { sourceManager.get(it) !is UnmeteredSource }
+            .maxOfOrNull { it.value.size } ?: 0
         if (maxUpdatesFromSource > MANGA_PER_SOURCE_QUEUE_WARNING_THRESHOLD) {
             toast(R.string.notification_size_warning, Toast.LENGTH_LONG)
         }