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/EventDispatcherInterface.php

@@ -0,0 +1,21 @@
+<?php
+declare(strict_types=1);
+
+namespace Psr\EventDispatcher;
+
+/**
+ * Defines a dispatcher for events.
+ */
+interface EventDispatcherInterface
+{
+    /**
+     * Provide all relevant listeners with an event to process.
+     *
+     * @param object $event
+     *   The object to process.
+     *
+     * @return object
+     *   The Event that was passed, now modified by listeners.
+     */
+    public function dispatch(object $event);
+}

docker/streamline-src/vendor/psr/event-dispatcher/src/ListenerProviderInterface.php

@@ -0,0 +1,19 @@
+<?php
+declare(strict_types=1);
+
+namespace Psr\EventDispatcher;
+
+/**
+ * Mapper from an event to the listeners that are applicable to that event.
+ */
+interface ListenerProviderInterface
+{
+    /**
+     * @param object $event
+     *   An event for which to return the relevant listeners.
+     * @return iterable[callable]
+     *   An iterable (array, iterator, or generator) of callables.  Each
+     *   callable MUST be type-compatible with $event.
+     */
+    public function getListenersForEvent(object $event) : iterable;
+}

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;
+}