Feature: #69794 - Support pecl-memcached in MemcachedBackend

Description

Support for the PECL module "memcached" has been added to the MemcachedBackend of the Caching Framework.

Impact

The MemcachedBackend checks if either "memcache" or "memcached" is installed. If both plugins are installed, the MemcachedBackend uses "memcache" over "memcached" to avoid being a breaking change. An integrator may set the option peclModule to use the preferred PECL module.

Example code:

$GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['my_memcached'] = [
	'frontend' => \TYPO3\CMS\Core\Cache\Frontend\VariableFrontend::class,
	'backend' => \TYPO3\CMS\Core\Cache\Backend\MemcachedBackend::class,
	'options' => [
		'peclModule' => 'memcached',
		'servers' => [
			'localhost',
			'server2:port'
		]
	]
];