Update DART deps to Focal

[playertr]

🦟 Bug fix

Fixes #1004

Summary

Within the Docker install_ign_deps.sh script, I updated DART dependencies from packages within the Bionic apt repositories to their Focal counterparts, at @chapulina 's suggestion from #1004 .

NOTE! : After making the changes, building ign_gazebo:base and ign_gazebo:nightly successfully completed. However, I have not been able to verify that the images function properly. I've been unsuccessfully debugging X forwarding to make glxgears or ign gazebo shapes.sdf work in the container with a GUI.

I'm opening this PR because I don't think it is related to my X11 bug, but I'd appreciate it if someone could verify that the created containers are correct.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge

[chapulina]

Thanks for the fix! Do you mind signing your commit for the DCO check?

For dealing with X issues, I recommend you take a look at https://github.com/adlarkin/ign-rocker. It was featured at this community meeting: https://www.youtube.com/watch?v=WcLj78PyrGk&list=PL6FI-gIL5jiGlch_uoSVNhCFaZb9eoj1J&index=3

[playertr]

Oops, I added a GPG key signature.

Rocker looks cool! I'll check out that video, which looks like it could supply some helpful context (I'm new to Docker). I assumed that the Docker image was intended to support OpenGL rendering, but it looks like it's meant to be a single node in a multi-container system. It looks like reading the Rocker docs could help me learn about how Docker and Ignition can work together.

[chapulina]

Oops, I added a GPG key signature.

I don't see the signature on the commit. See the details on the DCO checker: https://github.com/ignitionrobotics/ign-gazebo/pull/1005/checks?check_run_id=3478863349

I assumed that the Docker image was intended to support OpenGL rendering

I believe that may still depend on your host's NVIDIA drivers. I won't be able to test our Docker instructions soon to see if they can be updated further. But let's continue the conversation on #1004