Based on #31353 (sage --docbuild: Add options to list all documents), we can remove the issues with parallel (#31344) and serial (#31936) docbuild by restructuring the docbuild using make.

Blocker because it solves blocker issue #31936.

CC: @dimpase

Component: build

Author: John Palmieri, Matthias Koeppe

Branch: 53f260c

Reviewer: Matthias Koeppe, John Palmieri, Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/31948