Support for extraEnv in the `initContainer`

[qaoru]

DaemonSet template should support options to add extra env vars to initContainers / containers.

An example use-case that I have is an AKS cluster on a restricted network that should use an http proxy.
The HTTP proxy setting on AKS can apply http proxy variables to containers automatically but not on initContainers, hence the pod stays in CrashLoopBackOff since it cannot fetch the JFrog release.

[RobinDuhan]

Makes sense. Adding it as a feature request.