Add Idle Timeout support for NLB

[JoelSpeed]

What would you like to be added:

AWS recently announced the ability to configure the NLB TCP Idle Timeout. Up until now the default value has been 350 seconds, but for ELBs the default is 60 seconds, and is also configurable using the service.beta.kubernetes.io/aws-load-balancer-connection-idle-timeout annotation.

We should extend the annotation implementation so that it also works for the NLB implementation of EnsureLoadBalancer to gain access to this new functionality from AWS.

Why is this needed:

Support new features from AWS, improve consistency between ELB and NLB implementations.

/kind feature

[kmala]

/triage accepted