Add Postman Testing to helm chart

[rustyShacklefurd]

Problem

Have an automatic way to perform testing via postman against a deployment of hedera-json-rpc-relay.

Solution

Initially the idea of running this as cronjob works here. This would allow for configuring the test to run periodically plus then a job template is available to run these test on an on-demand basis as well.

Alternatives

Kubernetes has readiness, liveness, and startup gates now that can be utilized to run tests periodically and on redeployment. This could be a cleaner solution but requires some research on the new API available.