Support persistent volumes in Cosmos chains

[Inkvi]

[Anmol1696]

@Inkvi could we maybe move the same directives inside something like 'storage', we can still keep the names same.

The idea is to be able to make helm charts more modular, a flat hierarchy will get confusing to expand.

Helm charts usually also do this, have a look at 'persistence' directive in this chart: https://github.com/bitnami/charts/blob/main/bitnami/cassandra/values.yaml

Also for flags, the norm is to use '.enabled: true'.

[Anmol1696]

I can take care of it too, as part of beautification of the helm charts itself as well, if you want.

We can merge this as a feature, and then i can update it, but just wanted to let you know how i am thinking of this.