Build modified streamline images

The official image from streamline does not currently work for the arm64
platform. As a temporary measure, the source code and docker build scripts
have been lifted from the official images and are used to build locally.

Some additional modifications are made to reduce overall image size, these
are documented in docker/README.md

docker/streamline-src/vendor/psy/psysh/src/SystemEnv.php

@@ -0,0 +1,34 @@
+<?php
+
+/*
+ * This file is part of Psy Shell.
+ *
+ * (c) 2012-2023 Justin Hileman
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Psy;
+
+/**
+ * Environment variables implementation via getenv().
+ */
+class SystemEnv implements EnvInterface
+{
+    /**
+     * Get an environment variable by name.
+     *
+     * @return string|null
+     */
+    public function get(string $key)
+    {
+        if (isset($_SERVER[$key]) && $_SERVER[$key]) {
+            return $_SERVER[$key];
+        }
+
+        $result = \getenv($key);
+
+        return $result === false ? null : $result;
+    }
+}