Enhancement: reduce one layer of indirection in Looper's map about turtle

[YukunJ]

On March 10, 2023:

I experimented with the reduction of one layer of memory access in the Looper by stripping off the std::unique_ptr<Connection> to raw Connection *.

The performance gain is very marginal, at least on the experimental AWS machine. (before 59.3k v.s. after 59.6k).

I believe it is not worth it do make such a change, given that it complicates the life cycle management and introduces more pair of new and delete.