Provide base Docker images for download instead of building locally

[emersonknapp]

Description

On first use, building the rosdep collector and sysroot images take a long time (especially sysroot, since it's emulated). It would be nice to provide the undifferentiated portion of the build (e.g. rosdep, build tools) as a downloadable docker image, which should save a lot of time for the average case.

Related Issues

N/A

Completion Criteria

• Provide the following docker images in a Docker registry
  • rosdep - x86_64 only for all target operating systems
    • Ubuntu, Debian
    • comes out to 2 images
  • build tools - for the matrix of target architectures, OS, and ros versions
    • ros, ros2
    • Ubuntu, Debian
    • aarch64, armhf
    • comes out to 8 images
  • This is 10 total images to be hosted on a registry to cover the most common use cases
• When the needed image cannot be found,

Implementation Notes / Suggestions

• Separate build tools portion of sysroot.Dockerfile into a separate buildtools.Dockerfile
• Create a nightly GitHub Action on this repository building the rosdep.Dockerfile and buildtools.Dockerfile with the necessary matrix of build arguments
• Use Github Packages as a registry to store https://help.github.com/en/packages/using-github-packages-with-your-projects-ecosystem/configuring-docker-for-use-with-github-packages

Testing Notes / Suggestions

Run an additional nightly e2e test build, configured to be able to find the GitHub Package artifacts