CValidationInterface, mempool: add new callback to CValidationInterface

This commit adds a new callback `MempoolTransactionsRemovedForBlock` which notify
its listeners of the transactions that are removed from the mempool because a new
block is connected, along with the block height the transactions were removed.
The transactions are in `RemovedMempoolTransactionInfo` format.

`CTransactionRef`, base fee, virtual size, and height which the transaction was added
to the mempool are all members of the struct called `RemovedMempoolTransactionInfo`.

A struct `NewMempoolTransactionInfo`, which has fields similar to `RemovedMempoolTransactionInfo`,
will be added in a later commit, create a struct `TransactionInfo` with all similar fields.
They can both have a member with type `TransactionInfo`.

src/validationinterface.cpp

@@ -9,6 +9,7 @@
 #include <chain.h>
 #include <consensus/validation.h>
 #include <kernel/chain.h>
+#include <kernel/mempool_entry.h>
 #include <logging.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
@@ -233,6 +234,16 @@ void CMainSignals::BlockConnected(ChainstateRole role, const std::shared_ptr<con
                           pindex->nHeight);
 }
 
+void CMainSignals::MempoolTransactionsRemovedForBlock(const std::vector<RemovedMempoolTransactionInfo>& txs_removed_for_block, unsigned int nBlockHeight)
+{
+    auto event = [txs_removed_for_block, nBlockHeight, this] {
+        m_internals->Iterate([&](CValidationInterface& callbacks) { callbacks.MempoolTransactionsRemovedForBlock(txs_removed_for_block, nBlockHeight); });
+    };
+    ENQUEUE_AND_LOG_EVENT(event, "%s: block height=%s txs removed=%s", __func__,
+                          nBlockHeight,
+                          txs_removed_for_block.size());
+}
+
 void CMainSignals::BlockDisconnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex)
 {
     auto event = [pblock, pindex, this] {