Optimize SQLite3 access. Mainly separate read access from write access.

Based on tips from https://archive.is/Xfjh6#selection-257.0-278.0

persistence/artist_repository_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 
 	"github.com/fatih/structs"
+	"github.com/navidrome/navidrome/db"
 	"github.com/navidrome/navidrome/log"
 	"github.com/navidrome/navidrome/model"
 	"github.com/navidrome/navidrome/model/request"
@@ -18,7 +19,7 @@ var _ = Describe("ArtistRepository", func() {
 	BeforeEach(func() {
 		ctx := log.NewContext(context.TODO())
 		ctx = request.WithUser(ctx, model.User{ID: "userid"})
-		repo = NewArtistRepository(ctx, getDBXBuilder())
+		repo = NewArtistRepository(ctx, NewDBXBuilder(db.Db()))
 	})
 
 	Describe("Count", func() {