wallet: Cache scriptPubKeys for all DescriptorSPKMs

Have CWallet maintain a cache of all known scriptPubKeys for its
DescriptorSPKMs in order to improve performance of the functions that
require searching for scriptPubKeys.

Author: achow101

src/wallet/wallet.cpp

@@ -3891,6 +3891,8 @@ bool CWallet::ApplyMigrationData(MigrationData& data, bilingual_str& error)
         if (ExtractDestination(script, dest)) not_migrated_dests.emplace(dest);
     }
 
+    Assume(!m_cached_spks.empty());
+
     for (auto& desc_spkm : data.desc_spkms) {
         if (m_spk_managers.count(desc_spkm->GetID()) > 0) {
             error = _("Error: Duplicate descriptors created during migration. Your wallet may be corrupted.");
@@ -4337,6 +4339,9 @@ util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& walle
 
 void CWallet::CacheNewScriptPubKeys(const std::set<CScript>& spks, ScriptPubKeyMan* spkm)
 {
+    for (const auto& script : spks) {
+        m_cached_spks[script].push_back(spkm);
+    }
 }
 
 void CWallet::TopUpCallback(const std::set<CScript>& spks, ScriptPubKeyMan* spkm)

src/wallet/wallet.h

@@ -422,6 +422,9 @@ class CWallet final : public WalletStorage, public interfaces::Chain::Notificati
     // Same as 'AddActiveScriptPubKeyMan' but designed for use within a batch transaction context
     void AddActiveScriptPubKeyManWithDb(WalletBatch& batch, uint256 id, OutputType type, bool internal);
 
+    //! Cache of descriptor ScriptPubKeys used for IsMine. Maps ScriptPubKey to set of spkms
+    std::unordered_map<CScript, std::vector<ScriptPubKeyMan*>, SaltedSipHasher> m_cached_spks;
+
     /**
      * Catch wallet up to current chain, scanning new blocks, updating the best
      * block locator and m_last_block_processed, and registering for