Merge bitcoin#12639: Reduce cs_main lock in listunspent

a59dac3 refactor: Avoid extra lookups of mapAddressBook in listunspent RPC (João Barbosa)
d76962e rpc: Reduce cs_main lock in listunspent (João Barbosa)

Pull request description:

  On my system, where the wallet has 10000 unspents, the `cs_main` lock duration changed from 191ms to 36ms. The loop that generates the response takes around 155ms. So, the lock duration is reduced to around 20%.

Tree-SHA512: ddaae591f39da59a9d1a8e9ffe773d857687789476f566ca273d310ad531da6dacff80cac69f3334c601c251ac7c5ed4136656c725aa3d611c6bbf734111946e

src/wallet/rpcwallet.cpp

@@ -3623,9 +3623,13 @@ UniValue listunspent(const JSONRPCRequest& request)
 
     UniValue results(UniValue::VARR);
     std::vector<COutput> vecOutputs;
-    LOCK2(cs_main, pwallet->cs_wallet);
+    {
+        LOCK2(cs_main, pwallet->cs_wallet);
+        pwallet->AvailableCoins(vecOutputs, !include_unsafe, &coinControl, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount, nMinDepth, nMaxDepth);
+    }
+
+    LOCK(pwallet->cs_wallet);
 
-    pwallet->AvailableCoins(vecOutputs, !include_unsafe, &coinControl, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount, nMinDepth, nMaxDepth);
     for (const COutput& out : vecOutputs) {
         CTxDestination address;
         const CScript& scriptPubKey = out.tx->tx->vout[out.i].scriptPubKey;
@@ -3641,10 +3645,11 @@ UniValue listunspent(const JSONRPCRequest& request)
         if (fValidAddress) {
             entry.pushKV("address", EncodeDestination(address));
 
-            if (pwallet->mapAddressBook.count(address)) {
-                entry.pushKV("label", pwallet->mapAddressBook[address].name);
+            auto i = pwallet->mapAddressBook.find(address);
+            if (i != pwallet->mapAddressBook.end()) {
+                entry.pushKV("label", i->second.name);
                 if (IsDeprecatedRPCEnabled("accounts")) {
-                    entry.pushKV("account", pwallet->mapAddressBook[address].name);
+                    entry.pushKV("account", i->second.name);
                 }
             }