Break up workflows into reusable parts a bit more

[klauer]

Try composite actions again as part of shared workflows?

I seem to recall:

• I tried composite actions as part of the shared workflows without much luck
• Using bash scripts and other files in the shared pcds-ci-helpers isn't possible without cloning the repository inside the workflow (which seemed excessive)

I have some notes here about this:

• https://confluence.slac.stanford.edu/display/PCDS/Using+GitHub+Actions#UsingGitHubActions-Workflowre-usewith%22composite%22actions
• But I'm blanking on the details full now, though, so I'd like to re-investigate the use of composite actions to move closer to what @ZLLentz did in pcds-envs GHA migration