[doc] Improve Certificate Management documentation

[punamverma]

The Certificates Management section of DSS Deployment documentation only references the script dss-scripts.py used for certificate management of YugabyteDB. However, there is no mention of certificate management for CockroachDB. This could be confusing for users who directly refer to this section for Certificate Management, and are using CockroachDB.

Following the minikube instructions users eventually reach the Kubernetes Deployment section which mentions make-certs.py and apply-certs.sh scripts for CockroachDB. However, the minikube instructions are for DSS with YugaByteDB only and not for DSS using CockroachDB. It would be helpful to include instructions for CockroachDB as well.

Similarly, when following the terraform-aws-dss instructions, users come across mentions of using - make-certs.sh and apply-certs.sh scripts for cockroachDB. Note, repository contains make-certs.py and make-certs.sh.tmp in the repository. It would be beneficial to clarify how make-certs.sh is obtained or generated.

Thanks for all your efforts in making the documentation user-friendly.

[punamverma]

@barroco