Restore ObjectCache key creation

With the removal of inheritance between ObjectCache and CallbackCache,
the way cache keys are created changed for ObjectCache. Previously
CallbackCache was calling code in the ObjectCache class to create
a cache key based on the class name and method called.

This fix restores this by detecting if there is an object saved in the
PatternOptions, which is taken as an indicator we are dealing with the
ObjectCache use case.

As a side effect, this fix restores the ability to user-define the configuration
"object_key" in case multiple variants of the same class need to be
treated differently, as documented for ObjectCache pattern options.

resolves laminas#355

src/Pattern/CallbackCache.php

@@ -111,6 +111,15 @@ public function generateKey(callable $callback, array $args = []): string
      */
     protected function generateCallbackKey(callable $callback, array $args): string
     {
+
+        // Create a cache key for the ObjectCache use case.
+        $options = $this->getOptions();
+        if (is_object($options->getObject())) {
+            $callbackKey = md5($options->getObjectKey() . '::' . strtolower($callback[1]));
+            $argumentKey = $this->generateArgumentsKey($args);
+            return $callbackKey . $argumentKey;
+        }
+
         if (! is_callable($callback, false, $callbackKey)) {
             throw new Exception\InvalidArgumentException('Invalid callback');
         }