Add docker-in-docker feature to dev container

[westey-m]

Motivation and Context

Description

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

Adds Docker-in-Docker support to the .NET dev container so contributors can run Docker commands from within the container.

Changes:

• Enable the docker-in-docker devcontainer feature alongside existing CLI features.