library: keep display-only artists out of the artist lists

Filter the paged, search and home artist lists to artists referenced by the
plural credits, falling back to the full list while the relation tables are
still empty. Display names keep using the singular tag and navigation keeps
using the plural refs.

app/src/test/kotlin/com/subtracks/data/sync/SyncServiceTest.kt

@@ -27,6 +27,7 @@ import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.test.runTest
 import org.junit.After
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
@@ -58,7 +59,7 @@ class SyncServiceTest {
                 FakeMusicSource(
                     artists = listOf(artist("a1"), artist("a2")),
                     albums = listOf(album("al1")),
-                    songs = listOf(song("s1"), song("s2")),
+                    songs = listOf(song("s1"), song("s2").copy(artistId = "a2")),
                     playlists = listOf(playlist("p1")),
                     playlistSongs = listOf(PlaylistSong(1, "p1", "s1", 0)),
                 )
@@ -1064,6 +1065,37 @@ class SyncServiceTest {
             assertEquals("Zulu", db.libraryDao().songOnce(1, "s1")!!.artistSort)
         }
 
+    @Test
+    fun theArtistsListHidesNamesThatAreOnlyDisplayStrings() =
+        runTest {
+            insertSource()
+            val source =
+                FakeMusicSource(
+                    artists = listOf(artist("a1", "Alpha"), artist("combo", "Alpha & Beta")),
+                    albums = listOf(album("al1")),
+                    songs = listOf(song("s1")),
+                )
+
+            SyncService(db, source).sync()
+
+            assertEquals(
+                listOf("a1"),
+                db
+                    .libraryDao()
+                    .artistsByName(1, 0, "")
+                    .allRows()
+                    .map { it.id },
+            )
+            assertEquals(
+                listOf("a1"),
+                db
+                    .libraryDao()
+                    .searchArtists(1, "alpha", 10)
+                    .first()
+                    .map { it.id },
+            )
+        }
+
     @Test
     fun everyAlbumArtistAndTrackArtistReachesTheSharedAlbum() =
         runTest {