Configure Pod Disruption Budget for Ingesters in production jsonnet

[zalegrala]

We currently don't have a pod disruption budged set on the Ingesters in our microservices jsonnet, and we might want to consider adding one. This should signal to Kubernetes that we can only tolerate a single ingester down at a time.

Loki has something similar that we might want to model. https://github.com/grafana/loki/blob/cac0091dbea1660d1ebc855e621a6544e2eb3ea0/production/ksonnet/loki/ingester.libsonnet

ingester_pdb:
    podDisruptionBudget.new() +
    podDisruptionBudget.mixin.metadata.withName('loki-ingester-pdb') +
    podDisruptionBudget.mixin.metadata.withLabels({ name: 'loki-ingester-pdb' }) +
    podDisruptionBudget.mixin.spec.selector.withMatchLabels({ name: name }) +
    podDisruptionBudget.mixin.spec.withMaxUnavailable(0),

https://kubernetes.io/docs/reference/using-api/deprecation-guide/