Using node details in envoy_extra_static_clusters_json

#### Feature Description

I am running consul connect in k8s and I want to configure a static cluster in the sidecar that points to a telemetry collector running as a daemonset on each node. Consul knows the node name + ip but there is no way to get them into the static cluster definition, at least based on my reading of the docmentation (apologies if I have missed something).

I propose that the static cluster definition is pre-processed before sending to envoy to replace a token such as ${NODE_IP} with the actual node ip registered in consul.

#### Use Case(s)

To create static cluster definitions that point to a node-local address rather than a dns entry or a static cluster IP. Currently it is impossible to define a static cluster that points to a port on the same node because the required ip is not static.

The issue does not identify implementation files, tests, or an entry point. Start by tracing how envoy_extra_static_clusters_json is processed for Consul Connect sidecars, then define how the node name or IP is obtained and substituted; done means a node-local static cluster can be configured for a Kubernetes sidecar and is covered by tests.

Written by the indexing model from the issue text.