cysignals: Replace compile-time dependency on pari by run-time dispatch #32431
Description
Upstream issue:
CC: @kliem @tscrim @videlec @dimpase
Component: packages: standard
Work Issues: cypari2 and cysignals need new releases
Author: Jonathan Kliem
Branch/Commit: public/32431 @ 0353619
Issue created by migration from https://trac.sagemath.org/ticket/32431