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/psr/event-dispatcher/src/StoppableEventInterface.php

@@ -0,0 +1,26 @@
+<?php
+declare(strict_types=1);
+
+namespace Psr\EventDispatcher;
+
+/**
+ * An Event whose processing may be interrupted when the event has been handled.
+ *
+ * A Dispatcher implementation MUST check to determine if an Event
+ * is marked as stopped after each listener is called.  If it is then it should
+ * return immediately without calling any further Listeners.
+ */
+interface StoppableEventInterface
+{
+    /**
+     * Is propagation stopped?
+     *
+     * This will typically only be used by the Dispatcher to determine if the
+     * previous listener halted propagation.
+     *
+     * @return bool
+     *   True if the Event is complete and no further listeners should be called.
+     *   False to continue calling listeners.
+     */
+    public function isPropagationStopped() : bool;
+}