refactor: Move transaction_identifier.h to primitives

Moves the file from `src/util` to `src/primitives`. Now that the
refactor is complete, Txid and Wtxid are fundamental types, so it
makes sense for them to reside in `src/primitives`.

src/test/fuzz/hex.cpp

@@ -4,13 +4,13 @@
 
 #include <core_io.h>
 #include <primitives/block.h>
+#include <primitives/transaction_identifier.h>
 #include <pubkey.h>
 #include <rpc/util.h>
 #include <test/fuzz/fuzz.h>
 #include <uint256.h>
 #include <univalue.h>
 #include <util/strencodings.h>
-#include <util/transaction_identifier.h>
 
 #include <algorithm>
 #include <cassert>

src/test/transaction_tests.cpp

@@ -16,6 +16,7 @@
 #include <key.h>
 #include <policy/policy.h>
 #include <policy/settings.h>
+#include <primitives/transaction_identifier.h>
 #include <script/script.h>
 #include <script/script_error.h>
 #include <script/sigcache.h>
@@ -29,7 +30,6 @@
 #include <test/util/transaction_utils.h>
 #include <util/strencodings.h>
 #include <util/string.h>
-#include <util/transaction_identifier.h>
 #include <validation.h>
 
 #include <functional>

src/test/uint256_tests.cpp

@@ -2,11 +2,11 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <primitives/transaction_identifier.h>
 #include <streams.h>
 #include <test/util/setup_common.h>
 #include <uint256.h>
 #include <util/strencodings.h>
-#include <util/transaction_identifier.h>
 
 #include <boost/test/unit_test.hpp>