Adapt Service protocol from swift-service-lifecycle

[dkz2]

This PR address the need to integrate swift-service-lifecycle's Service protocol into our MemcachedConnection.
The incorporation of the Service protocol will ensure a unified and standardized lifecycle management for our Memcached service. This PR will close #36.

Motivation:
To adopt industry standards for service lifecycle management and improve the maintainability and operability of our MemcachedConnection. Incorporating the Service protocol enhances the way we manage the startup and shutdown procedures of the service.

Modifications:

• Implemented the Service protocol in MemcachedConnection.
• Updated our Program example to now use ServiceGroup initialization to include MemcachedConnection as a Service.

Results:
With the integration of the Service protocol, MemcachedConnection now benefits from standardized lifecycle management. This improves the reliability of the service and makes it easier to manage in production setups.

[FranzBusch]

We can use the shorter init here

Suggested change

	let serviceGroupConfiguration = ServiceGroupConfiguration(
	services: [ServiceGroupConfiguration.ServiceConfiguration(service: memcacheConnection)],
	gracefulShutdownSignals: [],
	cancellationSignals: [],
	logger: self.logger
	)
	// Initialize the service group
	let serviceGroup = ServiceGroup(configuration: serviceGroupConfiguration)
	// Initialize the service group
	let serviceGroup = ServiceGroup(services: memcacheConnection)