feat: add a woker mode (#1)

* refactor: better memory management

* wip

* tmp

* introduce a go-like api

* upgraded to PHP 8.2

* Fix thread safety issues

* fix tests

* wip

* refactor worker

* worker prototype

* fix populate env

* session

* improve tests

* fix Caddy tests

* refactor

testdata/server-variable.php

@@ -1,3 +1,7 @@
 <?php
 
-echo print_r($_SERVER);
+require_once __DIR__.'/_executor.php';
+
+return function () {
+    echo print_r($_SERVER);
+};