Add missing cdef method declarations (for Cython 3) #34257
Description
from #29863 comment:15
CC: @tscrim @kwankyu @tobiasdiez
Component: cython
Author: Matthias Koeppe
Branch/Commit: u/mkoeppe/add_missing_cdef_method_declarations__for_cython_3_ @ 9d89bdf
Issue created by migration from https://trac.sagemath.org/ticket/34257