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>