Provide PSR array cache and switch annotation reader to it

The annotation reader was using CachedReader which has been deprecated so we need to switch to PsrCachedReader
Since 2.0 doctrine/cache no longer provides implementations of caches so I also needed to implement a simple PSR array cache.
[MAILPOET-3892]

lib/Doctrine/Annotations/AnnotationReaderProvider.php

@@ -2,29 +2,28 @@
 
 namespace MailPoet\Doctrine\Annotations;
 
+use MailPoet\Doctrine\PSRArrayCache;
 use MailPoetVendor\Doctrine\Common\Annotations\AnnotationReader;
 use MailPoetVendor\Doctrine\Common\Annotations\AnnotationRegistry;
-use MailPoetVendor\Doctrine\Common\Annotations\CachedReader;
+use MailPoetVendor\Doctrine\Common\Annotations\PsrCachedReader;
-use MailPoetVendor\Doctrine\Common\Cache\ArrayCache;
 
 class AnnotationReaderProvider {
-  /** @var CachedReader */
+  /** @var PsrCachedReader */
   private $annotationReader;
 
   public function __construct() {
     // register annotation reader if doctrine/annotations package is installed
     // (i.e. in dev environment, on production metadata is dumped in the build)
-    $readAnnotations = class_exists(CachedReader::class) && class_exists(AnnotationReader::class);
+    $readAnnotations = class_exists(PsrCachedReader::class) && class_exists(AnnotationReader::class);
     if ($readAnnotations) {
       // autoload all annotation classes using registered loaders (Composer)
       // (needed for Symfony\Validator constraint annotations to be loaded)
       AnnotationRegistry::registerLoader('class_exists');
-      $this->annotationReader = new CachedReader(new AnnotationReader(), new ArrayCache());
+      $this->annotationReader = new PsrCachedReader(new AnnotationReader(), new PSRArrayCache());
     }
   }
 
-  /** @return CachedReader|null */
+  public function getAnnotationReader(): ?PsrCachedReader {
-  public function getAnnotationReader() {
     return $this->annotationReader;
   }
 }

lib/Doctrine/PSRArrayCache.php

@@ -0,0 +1,88 @@
+<?php
+
+namespace MailPoet\Doctrine;
+
+use MailPoetVendor\Psr\Cache\CacheItemInterface;
+use MailPoetVendor\Psr\Cache\CacheItemPoolInterface;
+
+class PSRArrayCache implements CacheItemPoolInterface {
+  /** @var mixed[] */
+  private $cache = [];
+
+  /**
+   * @inheritDoc
+   */
+  public function getItem($key) {
+    if (!is_string($key)) {
+      throw new PSRCacheInvalidArgumentException('Invalid key');
+    }
+    if (!$this->hasItem($key)) {
+      return new PSRCacheItem($key, false);
+    }
+    return new PSRCacheItem($key, $this->cache[$key]);
+  }
+
+  public function getItems(array $keys = []) {
+    return array_map([$this, 'getItem'], $keys);
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public function hasItem($key) {
+    return array_key_exists($key, $this->cache);
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public function clear() {
+    $this->cache = [];
+    return true;
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public function deleteItem($key) {
+    if (!is_string($key)) {
+      throw new PSRCacheInvalidArgumentException('Invalid key');
+    }
+    unset($this->cache[$key]);
+    return true;
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public function deleteItems(array $keys) {
+    try {
+      array_map([$this, 'deleteItem'], $keys);
+    } catch (PSRCacheInvalidArgumentException $e) {
+      return false;
+    }
+    return true;
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public function save(CacheItemInterface $item) {
+    $this->cache[$item->getKey()] = $item->get();
+    return true;
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public function saveDeferred(CacheItemInterface $item) {
+    return $this->save($item);
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public function commit() {
+    return true;
+  }
+}