Loki PodDisruptionBudget configuratation

Loki PDB configuration

Currently the PodDistruptionBudget templates for the loki read and write STSs hardcode a maximum of 1 unavailable pod. In the event that users have many replicas in their STS, having more lenient PDB settings is preferable, especially when draining nodes during worker upgrades.

Suggestion

Either allow users to drop the PDB spec directly into values, or maybe settings for maxUnavailable and minAvailable could be added at .Values.[write|read].podDisruptionBudget.