Prepend Docker Package with 'ci-'

[walshmm]

Is your feature request related to a problem? Please describe.
The packages(docker images) used for ci should be prepended with the prefix 'ci-' to help prevent confusion if someone stumbles upon them. This comes as a result of making these packages public facing as we wouldnt want to imply these are somehow prebuilt versions of qmcpack as opposed to utility images.

Describe the solution you'd like
Re-tag docker images, and update the github actions yml file with the new names.

Additional context
See above.