gh-119786: move frames documentation to InternalDocs and add details

[iritkatriel]

• Issue: create an internals documentation folder in the cpython repo #119786

[markshannon]

I've a few suggestions.

Also, FYI:

• f_globals and f_builtins are likely to be removed soon faster-cpython/ideas#661
• We may even move to a two-stack approach faster-cpython/ideas#675

[markshannon]

I don't think the instruction pointer belongs here (at least not conceptually).
I would add it to specials/linkage

[iritkatriel]

How about I change this line to
Execution state: evaluation stack, instruction pointer ?

It feels like instruction pointer is internal to the frame's working, rather than linking to external frames or objects.

[markshannon]

I think it would make sense to merge the "specials" and "linkage" sections. The only real "linkage" is the previous pointer.

So, maybe replace "specials and linkage" with "specials", and when specifically referring to "linkage", say previous poointer?

[markshannon]

Thanks