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

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

persistence/sql_bookmarks_test.go

@@ -3,6 +3,7 @@ package persistence
 import (
 	"context"
 
+	"github.com/navidrome/navidrome/db"
 	"github.com/navidrome/navidrome/log"
 	"github.com/navidrome/navidrome/model"
 	"github.com/navidrome/navidrome/model/request"
@@ -16,7 +17,7 @@ var _ = Describe("sqlBookmarks", func() {
 	BeforeEach(func() {
 		ctx := log.NewContext(context.TODO())
 		ctx = request.WithUser(ctx, model.User{ID: "userid"})
-		mr = NewMediaFileRepository(ctx, getDBXBuilder())
+		mr = NewMediaFileRepository(ctx, NewDBXBuilder(db.Db()))
 	})
 
 	Describe("Bookmarks", func() {