src: memory management using smart pointer

Introduced use of smart pointers instead of MallocedBuffer to manage
memory allocated in the cares library.

PR-URL: https://github.com/nodejs/node/pull/23628


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>