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/guzzlehttp/psr7/src/LazyOpenStream.php

@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GuzzleHttp\Psr7;
+
+use Psr\Http\Message\StreamInterface;
+
+/**
+ * Lazily reads or writes to a file that is opened only after an IO operation
+ * take place on the stream.
+ */
+final class LazyOpenStream implements StreamInterface
+{
+    use StreamDecoratorTrait;
+
+    /** @var string */
+    private $filename;
+
+    /** @var string */
+    private $mode;
+
+    /**
+     * @var StreamInterface
+     */
+    private $stream;
+
+    /**
+     * @param string $filename File to lazily open
+     * @param string $mode     fopen mode to use when opening the stream
+     */
+    public function __construct(string $filename, string $mode)
+    {
+        $this->filename = $filename;
+        $this->mode = $mode;
+
+        // unsetting the property forces the first access to go through
+        // __get().
+        unset($this->stream);
+    }
+
+    /**
+     * Creates the underlying stream lazily when required.
+     */
+    protected function createStream(): StreamInterface
+    {
+        return Utils::streamFor(Utils::tryFopen($this->filename, $this->mode));
+    }
+}