Refactor: executor: Avoid snprintf() in get_address_info()

To avoid the need to error-check snprintf() explicitly, which we have
not been doing.

Right now we can be sure port is at most 65536, but it's simpler not to
use that assumption in get_address_info() anyway. This extra allocation
shouldn't impact performance in any significant way.

Ref T974

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>