envFile support for system-extensions

[btrepp]

Feature Request

Talos extensions currently support setting env vars for the container, however there doesn't appear to be an 'envFile' equivalent.
This means extensions that require some sort of 'configuration' have to write their own wrappers

It would be great if there would be an enhancement to extensions that allows for 'envFiles'. That could set the containers environment.

Description

This was encountered in the below extension, where I wanted to allow consumers to configure things like a Tailscale key.
From : siderolabs/extensions#154

The workaround I used there was an existing exe inside the container, that forks out to the process after setting the environment. It's also possibly to write wrapper exe's that do similar.

Having this feature added would mean future extensions don't have to write wrappers as often, and also allow some already containerised friendly apps to work out of the box (eg ones that support env vars).

[frezbo]

This seems a valid ask 👍