Auto add private ip annotation to nodes

[rahulait]

We added support for specifying Private IP by annotation for VLAN / VPC in PR #141. We wanted to further enhance it and automatically add annotations to nodes with the backend private ip address. This PR enables automatically adding the annotation by looking at node's private ip-address.

Key points

Currently, linode nodebalancer doesn't support any subnet outside of 192.168.128.0/17. Once nodebalancer adds support for other subnets, we need to update linode-ccm to support that.

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[glennpratt]

Overall, excited to have this automated.

I would wire things up using the GetInstanceIPAddresses method (and running it through the cache too), then using the pattern Terraform and CAPL use.

I'd also drop the configuration flag. This pattern is pretty heavily used already. When NodeBalancers change to support other backends, other IP ranges or IPv6, I think changing the code and expecting users to update is better than trying to guess what config flags they need in advance.

[rahulait]

@glennpratt We now need this feature as we have already added support to use vpc specific ip's as internal ip's if the cluster is running within the VPC (to prevent cilium from caching incorrect ips). We now return two internal ips (first VPC ip, second 192.XX subnet ip). Without this PR, linode-ccm tries to use the first internal ip we have for node with nodebalancers and keeps failing. We'll set autoAnnotateNode to true when installing clusters within VPC and it will detect an ip on default private subnet ip address (192.168.128.0/17), annotate the node using it and then CCM can configure nodebalancers successfully.

[rahulait]

@glennpratt Removed the flags and now relying on the linode API response for the private IP. PTAL 🙏