Vault Use Passthrough IngressGateway in BigBang

Similar to Keycloak, create the following for the Vault package to configure and document using an Istio Passthrough IngressGateway when deployed via BigBang:

• BigBang chart values have ingress.gateway along with ingress.cert & ingress.key
• BigBang tests/test-values.yaml vault values pointed to utilize the passthrough Ingressgateway complete with certs
• Create an example values file for Vault passthrough iGW configuration at docs/example_configs/vault-dev-values.yaml