migrate: refactor examples to use the new FromFS function

migrate/example/cql/embed.go

@@ -0,0 +1,13 @@
+// Copyright (C) 2017 ScyllaDB
+// Use of this source code is governed by a ALv2-style
+// license that can be found in the LICENSE file.
+
+// +build all integration
+
+package cql
+
+import "embed"
+
+// Files contains *.cql schema migration files.
+//go:embed *.cql
+var Files embed.FS