fix: update total statements in the migration when it is being executed

The reason for this is that users are required to edit existing migration files to resolve partial failure issues. Without keeping total in sync, such migration would be considered still pending, because total != applied.
Issue: ariga#2455

sql/migrate/migrate.go

@@ -812,6 +812,12 @@ func (e *Executor) Execute(ctx context.Context, m File) (err error) {
 			Hash:        hash,
 		}
 	}
+
+	// Update total statements in the existing revision to support
+	// statement-level granularity in cases when users add new statements to
+	// existing migrations to resolve partial failures.
+	r.Total = len(stmts)
+
 	// Save once to mark as started in the database.
 	if err = e.writeRevision(ctx, r); err != nil {
 		return err