Add a new `info` property that holds the `meta.ModuleInfo` info
for the stage. This gives each instance of a stage access to
meta (or class) information about it, i.e. its schema, docs but,
more importantly, also its name and path to the executable.
Thefore the `name` property is coverted into a transient property
which access the `name` member of `info`.
Change the `formats/v1` load mechanism to carry a new `index`
argument which is used to load the `ModuleInfo` for each stage.
Adapt all tests to load the info as well when creating stages.
7a6c2df910