Fix Earthly/Dockerfile dichotomy

[Bckempa]

Currently some components use Earthly Earthfiles while others use Dockerfiles. Get everything within the same ecosystem.

On one hand, removing Earthly means more engineering work to replace the scripting and dependency resolution it currently provides. On the other, moving everything back to plain Docker/Make/Shell might be more familiar to most contributors.

[EzraBrooks]

Personally I'm in favor of migrating away from Earthly, I think it's too niche for an unfunded OSS project to rely on contributors to know.

Also, there's such massive room for improvement in the Dockerfiles and the Docker syntax included in the Earthfiles that we need to be more focused on supporting one system.

[Bckempa]

A discussion thread has been opened to weigh options.

[xfiderek]

• Adjust main spaceros image to the new build approach #158
  • Create lightweight, core image for spaceros #159
  • Need to pin the Navigation2 version number for stability docker#142 (will serve as a template for issues below)
    • Update moveit2 docker image to match the new build approach #161
    • Update space_robots demo to match the new build approach demos#27
    • Update nav2_demo to match the new build approach demos#28
    • Create a tutorial on building overlay workspace on top of spaceros #162
• Rename docker repo to stacks repo  #160

Issues on the same level can be executed in parallel. Levels outline dependencies (e.g. 159 depends on 158, and 161 depends on 142)