Trigger notice on memcached set failure

[KminekMatej]

• I found out Memcached is not storing some structure I wanted. I discovered that set() function fails, responding with false. Later I discovered reason using Memcached::getResultCode() which I found in phpDoc.

• This response, however is not handled in Nette. I suggest failure on write to cache should at least trigger notice for user.

I will gladly make a PR, but before I would like to know author's opinion.

Instead of

caching/src/Caching/Storages/MemcachedStorage.php

Line 169 in ceb814d

$this->memcached->set($key, $meta, $expire);

I would suggest something like:

		$stored = $this->memcached->set($key, $meta, $expire);
                
                if(!$stored){
                    trigger_error("Storing to memcached failed with error ".$this->memcached->getResultCode().": " . $this->memcached->getResultMessage(), E_USER_NOTICE);
                }

⚠️ Adding new Notice might consider that as a Breaking Change - Im not completely familiar with these internal rules.