Split fe_set_b32 into reducing and normalizing variants

src/tests_exhaustive.c

@@ -60,7 +60,7 @@ static void random_fe(secp256k1_fe *x) {
     unsigned char bin[32];
     do {
         secp256k1_testrand256(bin);
-        if (secp256k1_fe_set_b32(x, bin)) {
+        if (secp256k1_fe_set_b32_limit(x, bin)) {
             return;
         }
     } while(1);