have variant of extraInitContainers that uses tpl

[JonEngle]

Is your feature request related to a problem? Please describe.
I want to be able to pass in a string to get evaluated as a template for init containers instead of having to pass everything in as literals.

Describe the solution you'd like
It's a common approach to have a variable used as a provided template for specific blocks

Describe alternatives you've considered
Providing automation to helm that drives the init container configuration. Maybe cdk8s.

[TJM]

We would like this as well, if, for no other reason than to use the same ".Values.image.tag" as the main vault container, so that we don't need to download two different images.