gh-38433: Make # abs tol compare over the complex numbers
For calculations over complex numbers that generate numeric noise, one
tends to create small but non-zero imaginary parts. This PR updates the
"# abs tol" tolerance setting to work over the complex numbers, as the
"abs" suggests complex numbers. The real and imaginary parts are
compared separately.
The ordinary "# tol" and "# rel tol" are left as is.
Fixes #36631
URL: https://github.com/sagemath/sage/pull/38433
Reported by: Volker Braun
Reviewer(s): Dima Pasechnik
