Validate docker image tag is valid

[bloodearnest]

A user recently typo'd a few of their run commands like so:

run: r:analysis/data_prep_descrip.R

This mean the image name was parsed as r:analysis/data_prep_descrip.R rather than r, and produced an INTERNAL_ERROR

We should validate when parsing the yaml that the tag for images is valid. This will likely either mean figuring out explicit valid versions, or possibly more simply using a regex validation of the tag to match something like v\d{\.\d}*?

Context: https://bennettoxford.slack.com/archives/C01D7H9LYKB/p1714559913897309

[evansd]

Ah, I created an issue for this already but probably on the wrong repo in retrospect:

• Incorrect action syntax leads to an internal error job-runner#728