Merge bitcoin-core#1581: test, ci: Lower default iteration count to 16

0f73caf test, ci: Lower default iteration count to 16 (Hennadii Stepanov)

Pull request description:

  The number of test iterations in the CI remains the same.

  Resolves bitcoin-core#1561.

  ```
  $ ./build/src/tests
  test count = 16
  random seed = 59ea2b21267ec0ef0b4d13821292489f
  random run = 2936c044f82c7598a866869b9d954d42
  no problems found
  ```

ACKs for top commit:
  sipa:
    utACK 0f73caf
  jonasnick:
    ACK 0f73caf

Tree-SHA512: 84b265dc5d2780b3ea0a38f50ac8871d850ef2c97f33a0a5816baf20ac71c01db8b85696b343b089d7116d9cdb9450a6ca668229d95e54a39920d0e91a3127b3

.cirrus.yml

@@ -25,7 +25,7 @@ env:
   MUSIG: no
   ELLSWIFT: no
   ### test options
-  SECP256K1_TEST_ITERS:
+  SECP256K1_TEST_ITERS: 64
   BENCH: yes
   SECP256K1_BENCH_ITERS: 2
   CTIMETESTS: yes

.github/workflows/ci.yml

@@ -36,7 +36,7 @@ env:
   MUSIG: '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;
 
@@ -5544,7 +5544,7 @@ 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();
     }
 }