Merge #14838: Use const in COutPoint class

cf4b0327ed Use std::numeric_limits<UNSIGNED>::max()) instead of (UNSIGNED)-1 (practicalswift)
6b82fc59eb Use const in COutPoint class (Hennadii Stepanov)

Pull request description:

  Refactoring:
  - all cases of using `(uint32_t) -1` in `COutPoint` class are replaced with const;
  - also all remaining instances of `(UNSIGNED)-1` transformed to `std::numeric_limits<UNSIGNED>::max()` (by @practicalswift).

Tree-SHA512: fc7fe9838b6e5136d8b97ea3d6f64c4aaa1215f4369832df432cab017396620bb6e30520a64180ceab6de222562ac11eab243a78dfa5a658ba018835a34caa19

src/test/serialize_tests.cpp

@@ -200,7 +200,7 @@ BOOST_AUTO_TEST_CASE(varints)
     }
 
     for (uint64_t i = 0;  i < 100000000000ULL; i += 999999937) {
-        uint64_t j = -1;
+        uint64_t j = std::numeric_limits<uint64_t>::max();
         ss >> VARINT(j);
         BOOST_CHECK_MESSAGE(i == j, "decoded:" << j << " expected:" << i);
     }

src/test/sighash_tests.cpp

@@ -105,7 +105,7 @@ void static RandomTransaction(CMutableTransaction &tx, bool fSingle) {
         txin.prevout.hash = InsecureRand256();
         txin.prevout.n = InsecureRandBits(2);
         RandomScript(txin.scriptSig);
-        txin.nSequence = (InsecureRandBool()) ? InsecureRand32() : (unsigned int)-1;
+        txin.nSequence = (InsecureRandBool()) ? InsecureRand32() : std::numeric_limits<uint32_t>::max();
     }
     for (int out = 0; out < outs; out++) {
         tx.vout.push_back(CTxOut());