Add node outputs to the memcache module

[dkerr-ignw]

google_memcache_instance exports a memcache_nodes block that has:

node_id - Identifier of the Memcached node. The node id does not include project or location like the Memcached instance name.

zone - Location (GCP Zone) for the Memcached node.

port - The port number of the Memcached server on this node.

host - Hostname or IP address of the Memcached node used by the clients to connect to the Memcached server on this node.

state - Current state of the Memcached node.

This would be useful to upstream modules for things like assigning a DNS name to the IP address of the resulting nodes.

[comment-bot-dev]

Thanks for the PR! 🚀
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