fix(nmod): Add nmod_ctx to store is_prime

Author: oscarbenjamin

src/flint/types/nmod.pxd

@@ -2,8 +2,16 @@ from flint.flint_base.flint_base cimport flint_scalar
 from flint.flintlib.flint cimport mp_limb_t
 from flint.flintlib.nmod cimport nmod_t
 
-cdef int any_as_nmod(mp_limb_t * val, obj, nmod_t mod) except -1
+#cdef int any_as_nmod(mp_limb_t * val, obj, nmod_t mod) except -1
+cdef nmod_ctx any_as_nmod_ctx(obj)
+
+cdef class nmod_ctx:
+    cdef nmod_t mod
+    cdef bint _is_prime
+
+    cdef int any_as_nmod(self, mp_limb_t * val, obj) except -1
+    cdef nmod _new(self, mp_limb_t * val)
 
 cdef class nmod(flint_scalar):
     cdef mp_limb_t val
-    cdef nmod_t mod
+    cdef nmod_ctx ctx