cpdef functions using noexcept

[tornaria]

          regarding `cpdef` + `noexcept`:

$ git grep cpdef | grep noexcept | wc -l
341

so there are quite a few of these in the repo.

Originally posted by @dimpase in https://github.com/sagemath/sage/issues/37792#issuecomment-2058525010

It seems cpdef functions don't show warnings for misuse of noexcept. We should investigate about this.

[tornaria]

First thoughts:

• a cpdef function is equivalent to a cdef function + a def wrapper. I think the noexcept (or other except clauses) apply only to the cdef function since a def function must have the standard python semantics (iirc a python function always return a python object as a pointer with null meaning check for exceptions).
• by the same token, any cdef or cpdef function that returns a python object should not be noexcept as cython will ignore the noexcept (with a warning in the case of cdef functions, but maybe no warning for cpdef functions: should investigate and if so file an issue upstream)
• cpdef functions that return C types are in principle allowed to use noexcept (unless they call raise). In this case the def wrapper will convert the C type into a python object iiuc.
• Some c types that show up in the 341 matches: int, long, unsigned long, bint, size_t, double.

This leaves us with 28 cases to check:

$ git grep cpdef.*noexcept | grep -E -v "\<cpdef +(inline +)?(int|(unsigned )?long|bint|size_t|double) "
src/sage/graphs/bliss.pyx:cpdef canonical_form(G, partition=None, return_graph=False, use_edge_labels=True, certificate=False) noexcept:
src/sage/graphs/bliss.pyx:cpdef automorphism_group(G, partition=None, use_edge_labels=True) noexcept:
src/sage/libs/coxeter3/coxeter.pxd:    cpdef object full_context(self) noexcept
src/sage/libs/coxeter3/coxeter.pxd:    cpdef CoxGroup parent_group(self) noexcept
src/sage/libs/coxeter3/coxeter.pyx:    cpdef full_context(self) noexcept:
src/sage/libs/coxeter3/coxeter.pyx:    cpdef CoxGroup parent_group(self) noexcept:
src/sage/libs/gap/element.pxd:    cpdef UInt record_name_to_index(self, name) noexcept
src/sage/libs/gap/element.pyx:    cpdef UInt record_name_to_index(self, name) noexcept:
src/sage/libs/sirocco.pyx:cpdef list[list] contpath_mp(int deg, list values, RealNumber y0r, RealNumber y0i, int prec) noexcept:
src/sage/libs/sirocco.pyx:cpdef list[list] contpath_mp_comps(int deg, list values, RealNumber y0r, RealNumber y0i, int prec, list otherdegs, list othercoefs) noexcept:
src/sage/libs/sirocco.pyx:cpdef list[list] contpath(int deg, list values, double y0r, double y0i) noexcept:
src/sage/libs/sirocco.pyx:cpdef list[list] contpath_comps(int deg, list values, double y0r, double y0i, list otherdegrees, list othercoefs) noexcept:
src/sage/matrix/matrix_gfpn_dense.pxd:    cpdef fel_to_field(self, FEL x) noexcept
src/sage/matrix/matrix_gfpn_dense.pxd:    cpdef Matrix_gfpn_dense get_slice(self, Py_ssize_t i, Py_ssize_t j) noexcept
src/sage/matrix/matrix_gfpn_dense.pxd:    cpdef list _rowlist_(self, i, j=*) noexcept
src/sage/matrix/matrix_gfpn_dense.pxd:    cpdef Matrix_gfpn_dense _multiply_classical(Matrix_gfpn_dense self, Matrix_gfpn_dense right) noexcept
src/sage/matrix/matrix_gfpn_dense.pxd:    cpdef Matrix_gfpn_dense _multiply_strassen(Matrix_gfpn_dense self, Matrix_gfpn_dense right, cutoff=*) noexcept
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef fel_to_field(self, FEL x) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef fel_to_field(self, FEL x) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef Matrix_gfpn_dense get_slice(self, Py_ssize_t i, Py_ssize_t j) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef _richcmp_(left, right, int op) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef list _rowlist_(self, i, j=-1) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef _add_(self, right) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef _sub_(self, right) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef _lmul_(self, Element right) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef Matrix_gfpn_dense _multiply_classical(Matrix_gfpn_dense self, Matrix_gfpn_dense right) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef Matrix_gfpn_dense _multiply_strassen(Matrix_gfpn_dense self, Matrix_gfpn_dense right, cutoff=0) noexcept:
src/sage/matrix/matrix_gfpn_dense.pyx:    cpdef _echelon_in_place(self, str algorithm) noexcept: