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/sebastian/object-enumerator/src/Enumerator.php

@@ -0,0 +1,68 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of sebastian/object-enumerator.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace SebastianBergmann\ObjectEnumerator;
+
+use function array_merge;
+use function is_array;
+use function is_object;
+use SebastianBergmann\ObjectReflector\ObjectReflector;
+use SebastianBergmann\RecursionContext\Context;
+
+final class Enumerator
+{
+    /**
+     * @psalm-return list<object>
+     */
+    public function enumerate(array|object $variable, Context $processed = new Context): array
+    {
+        $objects = [];
+
+        if ($processed->contains($variable)) {
+            return $objects;
+        }
+
+        $array = $variable;
+
+        /* @noinspection UnusedFunctionResultInspection */
+        $processed->add($variable);
+
+        if (is_array($variable)) {
+            foreach ($array as $element) {
+                if (!is_array($element) && !is_object($element)) {
+                    continue;
+                }
+
+                /** @noinspection SlowArrayOperationsInLoopInspection */
+                $objects = array_merge(
+                    $objects,
+                    $this->enumerate($element, $processed)
+                );
+            }
+
+            return $objects;
+        }
+
+        $objects[] = $variable;
+
+        foreach ((new ObjectReflector)->getProperties($variable) as $value) {
+            if (!is_array($value) && !is_object($value)) {
+                continue;
+            }
+
+            /** @noinspection SlowArrayOperationsInLoopInspection */
+            $objects = array_merge(
+                $objects,
+                $this->enumerate($value, $processed)
+            );
+        }
+
+        return $objects;
+    }
+}