[ansible] add doc to stat module + function to display doc (#8382)

Hi,

I really would not like to see a separate doc page for the stat module
(the new stat.rst), and would like to see this accounted for in the
inline documentation for the stat module if possible.

Sorry I forgot to add it in the commit lines but I did remove it from
the equation. First timer mistakes..

I added the inline documentation as a list for the moment but I will
change for the simplest (maybe a dry list of the parameters as 'notes'
at the bottom) if you want.

Keeping this open to take a look at the ansible-doc parts and possibly
cherry-pick some things,but have not had a chance to look yet.

No problem, I can see by your activity on the list that you're kind of
busy, so take your time. The code isn't going anywhere anyway.

Thanks,