Refactor Common Code, used for creating Signers and Verifiers from JWK Set

[yogeshbdeshpande]

Currently we have the same code under test_common.go to construct Signers and Verifiers from JWK Key Set.

The same is used by CCA Token, PSA Token and EVCLI github repositories.

This issue tracks the change to either move them to a common repo and use the functions from "common"
repo in all libraries.

Alternatively Make them public interface from single base library like "psatoken" so that they can be reused in other repos.