Convert documentation to GAPDoc/AutoDoc

[fingolfin]

Replace the plain-TeX manual with GAPDoc XML built via AutoDoc, and drop
doc/make_doc for a makedoc.g in the package root. See
gap-system/gap#639.

Converted with dev/gapmacro2gapdoc.py from the GAP repository, which
corrected 27 declarations against the package's own source: most of the
operations were documented as functions, and the info classes as plain
variables. By hand:

• Ten operations are documented once for a group and once for a
  parametrised presentation, and two chapters both had a section called
  "Example". GAPDoc labels are book-wide, so these are labelled apart.

• The chapter reference read "p-power-poly-pcp-group", one letter short of
  the chapter, and GAP has since renamed the .gaprc file to gaprc.

• GeneratorsOfGroup and One belong to GAP; they are here.

• The recorded output of ParPresGlobalVar and the Schur extension examples
  predates a change in how a pp-presentation is represented. Refreshed
  from what GAP prints -- tst/manual.example-*.tst had been kept current
  while the manual had not, which is how it went unnoticed.

The \eqalign displays are now array environments, since GAPDoc's LaTeX
loads amssymb but not amsmath.

tst/manual.example-.tst are replaced by the generated
tst/symbcompcc0.tst. The test suite passes.

Co-Authored-By: Claude Opus 5 noreply@anthropic.com

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.47%. Comparing base (582aed6) to head (29b1528).

Additional details and impacted files

@@           Coverage Diff           @@
##           master       #8   +/-   ##
=======================================
  Coverage   57.47%   57.47%           
=======================================
  Files          21       21           
  Lines        6538     6538           
=======================================
  Hits         3758     3758           
  Misses       2780     2780           

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