Describe the bug

There two write operations in MemPool.TryRemoveUnVerified, and this function called by Blockchain.OnFillMemoryPool and MemPool.UpdatePoolForBlockPersisted.

Write operations triggered by MemPool.UpdatePoolForBlockPersisted is protected by _txRwLock, but by Blockchain.OnFillMemoryPool is not.

        internal bool TryRemoveUnVerified(UInt256 hash, [MaybeNullWhen(false)] out PoolItem? item)
        {
            if (!_unverifiedTransactions.TryGetValue(hash, out item))
                return false;

            _unverifiedTransactions.Remove(hash);
            _unverifiedSortedTransactions.Remove(item);
            return true;
        }

According to comments of _txRwLock, write operations should acquire write lock of _txRwLock.