To give due credit, this is an extension of the work begun by Kalpesh
Krishna to create action tasks. This is an upgrade to and
formalization of the file format, but built on the same foundation.
We would likely continue to support `actions.yml` in parallel with
`actions.json` until the latter is fully supported, then remove
creation of `actions.yml`. Since this is in-tree, though, we will
have decision tasks creating `actions.yml` for a year or two afterward
(admittedly just ESR for most of that time).