Feature description

Currently, Nebari deploys and configures dask-gateway automatically. However, not everyone using Nebari uses or is planning to use dask-gateway. We could have it be optional, just like other services (e.g., jhub-apps, argo, monitoring, etc...)

Value and/or benefit

Leaner deployment for users not planning to use dask-gateway

Anything else?

In order for this to not be a breaking change, it's important to keep dask-gateway enabled by default.