Moves the Program Dashboard APIs out of the deprecated remnants of the legacy learner dashboard, into the Programs djangoapp.
Keeps the old legacy routes for this API, left over from the deprecated remnants of the legacy learner dashboard, alongside future-proofed routes which will work when the deprecated, legacy Program Dashboard is eventually replaced with functionality in the Learner Dashboard MFE.
FIXES: APER-3949
The LMS `certificates` app `README` has been, and the
openedx core `credentials` and `programs` READMEs have been created.
This will clarify not only what the limited responsibilities
of each of these django apps is, but also the way they interact with
each other.
FIXES: APER-2929
