update makefile which generates charts schems with a modern helm schema tool

[danishedb]

We need to update the charts schema generate tool with the one actively maintained and being used in barman plugin chart

Problem:
Currently the tool which we are using to generate charts schema is not maintained please refer this schema-gen

Solution:
update the schema generation of cloudnative-pg and cluster with the one we are using in barman-plugin
Please refer this makefile