chore: switch database engine to sqlite (fixes #9954) (#9965)

Switch the database from LevelDB to SQLite, for greater stability and
simpler code.

Co-authored-by: Tommy van der Vorst <tommy@pixelspark.nl>
Co-authored-by: bt90 <btom1990@googlemail.com>

lib/api/api_auth_test.go

@@ -10,10 +10,9 @@ import (
 	"testing"
 	"time"
 
+	"github.com/syncthing/syncthing/internal/db"
+	"github.com/syncthing/syncthing/internal/db/sqlite"
 	"github.com/syncthing/syncthing/lib/config"
-	"github.com/syncthing/syncthing/lib/db"
-	"github.com/syncthing/syncthing/lib/db/backend"
-	"github.com/syncthing/syncthing/lib/events"
 )
 
 var guiCfg config.GUIConfiguration
@@ -131,8 +130,14 @@ func (c *mockClock) wind(t time.Duration) {
 func TestTokenManager(t *testing.T) {
 	t.Parallel()
 
-	mdb, _ := db.NewLowlevel(backend.OpenMemory(), events.NoopLogger)
-	kdb := db.NewNamespacedKV(mdb, "test")
+	mdb, err := sqlite.OpenTemp()
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		mdb.Close()
+	})
+	kdb := db.NewMiscDB(mdb)
 	clock := &mockClock{now: time.Now()}
 
 	// Token manager keeps up to three tokens with a validity time of 24 hours.