Allow changing of namespaces for BB apps

Feature Request

Allow BB users to override the target namespaces for all BB apps.

Why

To allow multi-tenancy for bigbang, the default namespaces (istio-system, anchore, gitlab, etc.) will need to be deployed into different (configurable) namespaces so that they don't collide with said namespaces that may already exist on a cluster.

What is the use case for the feature you are requesting? What are you trying to solve?

A customer who wants us to deploy our system onto their cluster will already have certain BB applications on said cluster. To be able to deploy our system (which utilizes bigbang), we will need to change the namespaces to separate ourselves from what may already be on the cluster.

Proposed Solution

Allow value overrides for all BB apps so that when one deploys BB, the necessary objects (Helm release's target namespaces, secrets, EnvoyFilter, any Objects, etc.) will use the namespace in the values overrides instead of the hardcoded values. For example, instead of anchore, we could do jaic-anchore, and gitlab would jaic-gitlab (or whatever we want to call it).