Make MiniMinerMempoolEntry fields private

Follow-up from #27021: accessing of fields in MiniMinerMempoolEntry was
done inconsistently. Even though we had a getter, we would directly
write to the fields when we needed to update them.
This commits sets the fields to private and introduces a method for
updating the ancestor information in transactions using the same method
name as used for Mempool Entries.

src/node/mini_miner.cpp

@@ -169,9 +169,8 @@ void MiniMiner::DeleteAncestorPackage(const std::set<MockEntryMap::iterator, Ite
         for (auto& descendant : it->second) {
             // If these fail, we must be double-deducting.
             Assume(descendant->second.GetModFeesWithAncestors() >= anc->second.GetModifiedFee());
-            Assume(descendant->second.vsize_with_ancestors >= anc->second.GetTxSize());
-            descendant->second.fee_with_ancestors -= anc->second.GetModifiedFee();
-            descendant->second.vsize_with_ancestors -= anc->second.GetTxSize();
+            Assume(descendant->second.GetSizeWithAncestors() >= anc->second.GetTxSize());
+            descendant->second.UpdateAncestorState(-anc->second.GetTxSize(), -anc->second.GetModifiedFee());
         }
     }
     // Delete these entries.

src/node/mini_miner.h

@@ -19,12 +19,13 @@ class MiniMinerMempoolEntry
     const CAmount fee_individual;
     const CTransactionRef tx;
     const int64_t vsize_individual;
+    CAmount fee_with_ancestors;
+    int64_t vsize_with_ancestors;
 
 // This class must be constructed while holding mempool.cs. After construction, the object's
 // methods can be called without holding that lock.
+
 public:
-    CAmount fee_with_ancestors;
-    int64_t vsize_with_ancestors;
     explicit MiniMinerMempoolEntry(CTxMemPool::txiter entry) :
         fee_individual{entry->GetModifiedFee()},
         tx{entry->GetSharedTx()},
@@ -38,6 +39,10 @@ public:
     int64_t GetTxSize() const { return vsize_individual; }
     int64_t GetSizeWithAncestors() const { return vsize_with_ancestors; }
     const CTransaction& GetTx() const LIFETIMEBOUND { return *tx; }
+    void UpdateAncestorState(int64_t vsize_change, CAmount fee_change) {
+        vsize_with_ancestors += vsize_change;
+        fee_with_ancestors += fee_change;
+    }
 };
 
 // Comparator needed for std::set<MockEntryMap::iterator>