test, ci: Lower default iteration count to 16

The number of test iterations in the CI remains unchanged.

Additionally, the minimum iteration counts to enable the
`test_ecmult_constants_2bit` test is adjusted from 35 to 16, so it is
run by default.

.cirrus.yml

@@ -24,7 +24,7 @@ env:
   SCHNORRSIG: no
   ELLSWIFT: no
   ### test options
-  SECP256K1_TEST_ITERS:
+  SECP256K1_TEST_ITERS: 64
   BENCH: yes
   SECP256K1_BENCH_ITERS: 2
   CTIMETESTS: yes

.github/workflows/ci.yml

@@ -35,7 +35,7 @@ env:
   SCHNORRSIG: 'no'
   ELLSWIFT: 'no'
   ### test options
-  SECP256K1_TEST_ITERS:
+  SECP256K1_TEST_ITERS: 64
   BENCH: 'yes'
   SECP256K1_BENCH_ITERS: 2
   CTIMETESTS: 'yes'

src/tests.c

@@ -37,7 +37,7 @@
 
 #define CONDITIONAL_TEST(cnt, nam) if (COUNT < (cnt)) { printf("Skipping %s (iteration count too low)\n", nam); } else
 
-static int COUNT = 64;
+static int COUNT = 16;
 static secp256k1_context *CTX = NULL;
 static secp256k1_context *STATIC_CTX = NULL;
 
@@ -5515,7 +5515,7 @@ static void run_ecmult_constants(void) {
         test_ecmult_constants_sha(1607366309u, 2048, expected32_8bit8);
     }
 
-    CONDITIONAL_TEST(35, "test_ecmult_constants_2bit") {
+    CONDITIONAL_TEST(16, "test_ecmult_constants_2bit") {
         test_ecmult_constants_2bit();
     }
 }