Merge #17905: gui: Avoid redundant tx status updates

96cb597325 gui: Avoid redundant tx status updates (Russell Yanofsky)

Pull request description:

  This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10).

  In `TransactionTablePriv::index`, avoid calling `interfaces::Wallet::tryGetTxStatus` if the status is up to date as of the most recent `NotifyBlockTip` notification.  Store height from the most recent notification in a new `ClientModel::cachedNumBlocks` variable in order to check this.

  This avoids floods of IPC traffic from `tryGetTxStatus` with #10102 when there are a lot of transactions. It might also make the GUI a little more efficient even when there is no IPC.

ACKs for top commit:
  promag:
    Code review ACK 96cb597325.
  hebasto:
    ACK 96cb597325

Tree-SHA512: fce597bf52a813ad4923110d0a39229ea09e1631e0d580ea18cffb09e58cdbb4b111a40a9a9270ff16d8163cd47b0bd9f1fe7e3a6c7ebb19198f049f8dd1aa46

src/qt/clientmodel.cpp

@@ -105,6 +105,14 @@ int64_t ClientModel::getHeaderTipTime() const
     return cachedBestHeaderTime;
 }
 
+int ClientModel::getNumBlocks() const
+{
+    if (m_cached_num_blocks == -1) {
+        m_cached_num_blocks = m_node.getNumBlocks();
+    }
+    return m_cached_num_blocks;
+}
+
 void ClientModel::updateNumConnections(int numConnections)
 {
     Q_EMIT numConnectionsChanged(numConnections);
@@ -241,6 +249,8 @@ static void BlockTipChanged(ClientModel *clientmodel, bool initialSync, int heig
         // cache best headers time and height to reduce future cs_main locks
         clientmodel->cachedBestHeaderHeight = height;
         clientmodel->cachedBestHeaderTime = blockTime;
+    } else {
+        clientmodel->m_cached_num_blocks = height;
     }
 
     // During initial sync, block notifications, and header notifications from reindexing are both throttled.