Cilium Feature Proposal

Is your proposed feature related to a problem?
Not really a bug, but a usability CFP.

Describe the feature you'd like
As of right now I have no easy way to detect that IPs are about to run out. There's a metric called cilium_ipam_capacity which is remaining IPs allocated to the node, but it doesn't take into account that the operator in multi-pool mode can allocate more IP subnets to each node.

I am not the first one to ask this - there was #25470 (comment) but I couldn't find any relevant issue from that comment.

(Optional) Describe your proposed solution
A metric called cilium_remaining_ips{pool="..."} for each pool (or some similar sounding metric name), either listing the amount of subnets it can still allocate or IP count it can allocate.