Docker ubuntu 18.04 support and static execs

[nilsdeppe]

Proposed changes

This adds most of the remaining code needed to CD the CCE executables.

The container is already push to the Dockerhub sxscollaboration image. I previously tested on my fork.

Upgrade instructions

Code review checklist

• [ ] The code is documented and the documentation renders correctly. Run make doc to generate the documentation locally into BUILD_DIR/docs/html. Then open index.html.
• [ ] The code follows the stylistic and code quality guidelines listed in the code review guide.
• [ ] The PR lists upgrade instructions and is labeled bugfix or new feature if appropriate.

Further comments

[nilsdeppe]

I've rebased this and set up auto deployment. I'm doing a final test on my fork to make sure it's working correctly, but I expect anything wrong would be a small typo in the last step of testing the CCE output is correct. This now bundles the CharacteristicExtract and ReduceCceWoldtube executables along with a BondiSachsR0200.h5 worldtube file, expected output file, and a python script that checks that things went okay. The last 3 parts are housed in our Google Drive since that was easiest to get working quick.

edit:

The release on my fork is running at https://github.com/nilsdeppe/spectre/actions/runs/9374720262/job/25811397363

[nilsdeppe]

This successfully deployed the executables on my fork. https://github.com/nilsdeppe/spectre/releases/tag/v2024.06.04.013

[nilsvu]

You can squash the fixups 👍

[nilsdeppe]

I've squashed, rebased, and squashed in a few of the other changes discussed. I think the bigger thing I'm hesitant to do is the workflow_call part. I'd tried something like that previous and must've done something wrong because it didn't work at all as expected.

[nilsdeppe]

I squashed the --only-binary change