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/phpunit/php-invoker/src/exceptions/Exception.php

@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-invoker.
+ *
+ * (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\Invoker;
+
+use Throwable;
+
+interface Exception extends Throwable
+{
+}

docker/streamline-src/vendor/phpunit/php-invoker/src/exceptions/ProcessControlExtensionNotLoadedException.php

@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-invoker.
+ *
+ * (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\Invoker;
+
+use RuntimeException;
+
+final class ProcessControlExtensionNotLoadedException extends RuntimeException implements Exception
+{
+}

docker/streamline-src/vendor/phpunit/php-invoker/src/exceptions/TimeoutException.php

@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-invoker.
+ *
+ * (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\Invoker;
+
+use RuntimeException;
+
+final class TimeoutException extends RuntimeException implements Exception
+{
+}