mempool: log/halt when CalculateMemPoolAncestors fails unexpectedly

When CalculateMemPoolAncestors fails unexpectedly (e.g. it exceeds
ancestor/descendant limits even though we expect no limits to be applied),
add an error log entry for increased visibility. For debug builds,
the application will even halt completely since this is not supposed
to happen.

src/node/miner.cpp

@@ -394,8 +394,7 @@ void BlockAssembler::addPackageTxs(const CTxMemPool& mempool, int& nPackagesSele
             continue;
         }
 
-        auto ancestors_result{mempool.CalculateMemPoolAncestors(*iter, CTxMemPool::Limits::NoLimits(), /*fSearchForParents=*/false)};
-        auto ancestors{std::move(ancestors_result).value_or(CTxMemPool::setEntries{})};
+        auto ancestors{mempool.AssumeCalculateMemPoolAncestors(__func__, *iter, CTxMemPool::Limits::NoLimits(), /*fSearchForParents=*/false)};
 
         onlyUnconfirmed(ancestors);
         ancestors.insert(iter);