Allow extensions to be run when Talos platform is container

[mattiascockburn]

Feature Request

Description

Currently no extensions work when Talos is running inside a container, as implemented in https://github.com/siderolabs/talos/blob/7b37e5b63d54c2d197336e4fbee941fa5f2423c0/internal/app/machined/pkg/controllers/runtime/extension_service_config_files.go#L59

We'd like to be able to test extensions like our custom code in a containerized Talos but are currently forced to run a custom fork with the conditional removed for this to work.