Improve lifetime management around the uv loop

We have several raw pointers in our tcp handlers (and IO threads) which use the uv loop to manage their lifetime (eg `uv_getaddrinfo_t`).

A better approach would be to have these objects within shared pointers in some higher level collection.
This will also make clang-tidy happier.

Start by locating the TCP handlers, IO-thread code, and uses of uv_getaddrinfo_t that rely on the uv loop for lifetime management. Map the current raw-pointer ownership before evaluating a higher-level shared-pointer collection; done means the relevant objects use the proposed ownership approach and clang-tidy no longer reports the lifetime issues.

Written by the indexing model from the issue text.