Tunable znode size for helm chart

Pinot actually requires much larger znode size limit comparing to the default settings.
We need to make this setting configurable and put a good default value.

Start by locating the Pinot Helm chart and the current znode size configuration or default settings. Determine where the value is defined and how chart users can override it, then verify the rendered chart uses a configurable setting with a larger default appropriate for Pinot.

Written by the indexing model from the issue text.