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/Rfc7230.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GuzzleHttp\Psr7;
+
+/**
+ * @internal
+ */
+final class Rfc7230
+{
+    /**
+     * Header related regular expressions (based on amphp/http package)
+     *
+     * Note: header delimiter (\r\n) is modified to \r?\n to accept line feed only delimiters for BC reasons.
+     *
+     * @see https://github.com/amphp/http/blob/v1.0.1/src/Rfc7230.php#L12-L15
+     *
+     * @license https://github.com/amphp/http/blob/v1.0.1/LICENSE
+     */
+    public const HEADER_REGEX = "(^([^()<>@,;:\\\"/[\]?={}\x01-\x20\x7F]++):[ \t]*+((?:[ \t]*+[\x21-\x7E\x80-\xFF]++)*+)[ \t]*+\r?\n)m";
+    public const HEADER_FOLD_REGEX = "(\r?\n[ \t]++)";
+}