istio: Install stats monitor and DestinationRule for buildkitd
Install a PodMonitor
to monitor all Istio/Envoy proxies and gather
metrics into the Prometheus instance deployed by kube-prometheus-stack.
Note this is necessary since we're using kube-prometheus-stack and not
the Prometheus provided by Istio.
Limit concurrent buildkitd connections to 4 for now using a
DestinationRule
. We'll get the connection saturation metric working
and suss out a better limit later.
Bug: T327416