prefixed-cache and namespaced-cache issues with ApcuCachePool

[aldas]

I'm trying to namespace/prefix apcu pool but I'm running into different problems due not implemented interfaces.

1. creating namespaced apcu pool fails

    return new NamespacedCachePool(new ApcCachePool(), $prefix);

because NamespacedCachePool constructor takes in HierarchicalPoolInterface which ApcCachePool does not implement

2. If I would like to use tags with NamespacedCachePool or NamespacedCachePool which wrap some Pool that implements TaggableCacheItemPoolInterface but this is not possible

$cache = new PrefixedCachePool(new ApcCachePool(), 'prefix');
...
$cache->invalidateTag('myAwesomeTag');

Call to undefined method Cache\Prefixed\PrefixedCachePool::invalidateTag()