Fix _real_escape() implementation as per WPDB

Author: JanJakes

.github/workflows/wp-tests-phpunit-run.js

@@ -54,9 +54,6 @@ const expectedFailures = [
 	'Tests_DB::test_charset_switched_to_utf8mb4',
 	'Tests_DB::test_close',
 	'Tests_DB::test_delete_value_too_long_for_field with data set "too long"',
-	'Tests_DB::test_escape_and_prepare with data set #0',
-	'Tests_DB::test_escape_and_prepare with data set #1',
-	'Tests_DB::test_escape_and_prepare with data set #2',
 	'Tests_DB::test_has_cap',
 	'Tests_DB::test_insert_value_too_long_for_field with data set "too long"',
 	'Tests_DB::test_mysqli_flush_sync',

wp-includes/sqlite/class-wp-sqlite-db.php

@@ -107,7 +107,8 @@ public function _real_escape( $data ) {
 		if ( ! is_scalar( $data ) ) {
 			return '';
 		}
-		return addslashes( $data );
+		$escaped = addslashes( $data );
+		return $this->add_placeholder_escape( $escaped );
 	}
 
 	/**