refactor: Add LIFETIMEBOUND to all (w)txid getters

Then, use the compiler warnings to create copies only where needed.

Also, fix iwyu includes while touching the includes.

src/wallet/test/group_outputs_tests.cpp

@@ -40,7 +40,7 @@ static void addCoin(CoinsResult& coins,
     tx.vout[0].nValue = nValue;
     tx.vout[0].scriptPubKey = GetScriptForDestination(dest);
 
-    const uint256& txid = tx.GetHash();
+    const auto txid{tx.GetHash().ToUint256()};
     LOCK(wallet.cs_wallet);
     auto ret = wallet.mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(txid), std::forward_as_tuple(MakeTransactionRef(std::move(tx)), TxStateInactive{}));
     assert(ret.second);

src/wallet/test/wallet_tests.cpp

@@ -963,7 +963,7 @@ BOOST_FIXTURE_TEST_CASE(wallet_sync_tx_invalid_state_test, TestingSetup)
     mtx.vin.clear();
     mtx.vin.emplace_back(tx_id_to_spend, 0);
     wallet.transactionAddedToMempool(MakeTransactionRef(mtx));
-    const uint256& good_tx_id = mtx.GetHash();
+    const auto good_tx_id{mtx.GetHash().ToUint256()};
 
     {
         // Verify balance update for the new tx and the old one