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-code-coverage/src/Util/Filesystem.php

@@ -0,0 +1,37 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-code-coverage.
+ *
+ * (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\CodeCoverage\Util;
+
+use function is_dir;
+use function mkdir;
+use function sprintf;
+
+/**
+ * @internal This class is not covered by the backward compatibility promise for phpunit/php-code-coverage
+ */
+final class Filesystem
+{
+    /**
+     * @throws DirectoryCouldNotBeCreatedException
+     */
+    public static function createDirectory(string $directory): void
+    {
+        $success = !(!is_dir($directory) && !@mkdir($directory, 0777, true) && !is_dir($directory));
+
+        if (!$success) {
+            throw new DirectoryCouldNotBeCreatedException(
+                sprintf(
+                    'Directory "%s" could not be created',
+                    $directory
+                )
+            );
+        }
+    }
+}

docker/streamline-src/vendor/phpunit/php-code-coverage/src/Util/Percentage.php

@@ -0,0 +1,59 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-code-coverage.
+ *
+ * (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\CodeCoverage\Util;
+
+use function sprintf;
+
+/**
+ * @internal This class is not covered by the backward compatibility promise for phpunit/php-code-coverage
+ */
+final class Percentage
+{
+    private readonly float $fraction;
+    private readonly float $total;
+
+    public static function fromFractionAndTotal(float $fraction, float $total): self
+    {
+        return new self($fraction, $total);
+    }
+
+    private function __construct(float $fraction, float $total)
+    {
+        $this->fraction = $fraction;
+        $this->total    = $total;
+    }
+
+    public function asFloat(): float
+    {
+        if ($this->total > 0) {
+            return ($this->fraction / $this->total) * 100;
+        }
+
+        return 100.0;
+    }
+
+    public function asString(): string
+    {
+        if ($this->total > 0) {
+            return sprintf('%01.2F%%', $this->asFloat());
+        }
+
+        return '';
+    }
+
+    public function asFixedWidthString(): string
+    {
+        if ($this->total > 0) {
+            return sprintf('%6.2F%%', $this->asFloat());
+        }
+
+        return '';
+    }
+}