This change extracts the functionality of reading an `action.y(a)ml` or
creation of a `(Synthetic Action)` into its own type to enable better
unit testing / mocking of those IO operations.
This is done in preparation for the implementation of pre/post action
support in act.
Co-authored-by: Markus Wolf <markus.wolf@new-work.se>
Co-authored-by: Markus Wolf <markus.wolf@new-work.se>
