Polymorphic refactor + improvements to select sql rewriting

pg4wp/rewriters/ShowTablesSQLRewriter.php

@@ -0,0 +1,9 @@
+<?php
+
+class ShowTablesSQLRewriter extends AbstractSQLRewriter
+{
+    public function rewrite(): string
+    {
+        return 'SELECT tablename FROM pg_tables WHERE schemaname = \'public\';';
+    }
+}