refactor: Make CTransaction constructor explicit

It involves calculating two hashes, so the performance impact should be
made explicit.

Also, add the module to iwyu.

src/primitives/transaction.cpp

@@ -7,10 +7,15 @@
 
 #include <consensus/amount.h>
 #include <hash.h>
+#include <script/script.h>
+#include <serialize.h>
 #include <tinyformat.h>
+#include <uint256.h>
 #include <util/strencodings.h>
+#include <version.h>
 
-#include <assert.h>
+#include <cassert>
+#include <stdexcept>
 
 std::string COutPoint::ToString() const
 {

src/primitives/transaction.h

@@ -6,13 +6,21 @@
 #ifndef BITCOIN_PRIMITIVES_TRANSACTION_H
 #define BITCOIN_PRIMITIVES_TRANSACTION_H
 
-#include <stdint.h>
 #include <consensus/amount.h>
+#include <prevector.h>
 #include <script/script.h>
 #include <serialize.h>
 #include <uint256.h>
 
+#include <cstddef>
+#include <cstdint>
+#include <ios>
+#include <limits>
+#include <memory>
+#include <string>
 #include <tuple>
+#include <utility>
+#include <vector>
 
 /**
  * A flag that is ORed into the protocol version to designate that a transaction
@@ -303,7 +311,7 @@ private:
 public:
     /** Convert a CMutableTransaction into a CTransaction. */
     explicit CTransaction(const CMutableTransaction& tx);
-    CTransaction(CMutableTransaction&& tx);
+    explicit CTransaction(CMutableTransaction&& tx);
 
     template <typename Stream>
     inline void Serialize(Stream& s) const {
@@ -368,7 +376,7 @@ struct CMutableTransaction
     int32_t nVersion;
     uint32_t nLockTime;
 
-    CMutableTransaction();
+    explicit CMutableTransaction();
     explicit CMutableTransaction(const CTransaction& tx);
 
     template <typename Stream>