Passthrough istio.enabled and istio.injection from bigbang

1. The curl statements to istio proxy need to be made conditional on isito.enabled and istio.injection in the following jobs
   chart/templates/bigbang/proxy.yaml
   chart/templates/bigbang/repos.yaml
   chart/templates/bigbang/saml.yaml
   see example from prometheus
   https://repo1.dso.mil/platform-one/big-bang/apps/core/monitoring/-/blob/main/chart/templates/prometheus-operator/admission-webhooks/job-patch/job-patchWebhook.yaml#L52

2. BigBang nexus template needs to pass these values down to the nexus package. And the nexus namespace needs to use dig for the istio injection so that is can be toggled off.
   see example from gitlab
   https://repo1.dso.mil/platform-one/big-bang/bigbang/-/blob/master/chart/templates/gitlab/namespace.yaml#L9