keypool: Move opportunistic TopUps from LegacyScriptPubKeyMan to CWallet and ReserveDestination

An opportunistic TopUp is moved from LegacyScriptPubKeyMan::GetNewDestination
to CWallet::GetNewDestination. Another opportunistic TopUp is moved from
LegacyScriptPubKeyMan::ReserveKeyFromKeyPool (called by LegacyScriptPubKeyMan::GetReservedDestination)
to ReserveDestination::GetReservedDestination.

Moving opportunistic TopUps ensures that ScriptPubKeyMans will always
be topped up before requesting Destinations from them as we cannot
always rely on future ScriptPubKeyMan implementaions topping up internally.
As such, it is also unnecessary to keep the TopUp calls in the
LegacyScriptPubKeyMan functions so they are moved.

This does not change behavior as TopUp calls are moved up the call stack.

Author: achow101

src/wallet/scriptpubkeyman.cpp

@@ -14,7 +14,6 @@
 bool LegacyScriptPubKeyMan::GetNewDestination(const OutputType type, CTxDestination& dest, std::string& error)
 {
     error.clear();
-    TopUp();
 
     // Generate a new key that is added to wallet
     CPubKey new_key;
@@ -1147,8 +1146,6 @@ bool LegacyScriptPubKeyMan::ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& key
     {
         LOCK(cs_wallet);
 
-        TopUp();
-
         bool fReturningInternal = fRequestedInternal;
         fReturningInternal &= (IsHDEnabled() && m_storage.CanSupportFeature(FEATURE_HD_SPLIT)) || m_storage.IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
         bool use_split_keypool = set_pre_split_keypool.empty();

src/wallet/wallet.cpp

@@ -3109,6 +3109,7 @@ bool CWallet::GetNewDestination(const OutputType type, const std::string label,
     bool result = false;
     auto spk_man = m_spk_man.get();
     if (spk_man) {
+        spk_man->TopUp();
         result = spk_man->GetNewDestination(type, dest, error);
     }
     if (result) {
@@ -3302,6 +3303,8 @@ bool ReserveDestination::GetReservedDestination(CTxDestination& dest, bool inter
 
     if (nIndex == -1)
     {
+        m_spk_man->TopUp();
+
         CKeyPool keypool;
         if (!m_spk_man->GetReservedDestination(type, internal, nIndex, keypool)) {
             return false;