SRV resolution is not thread-safe or fully windows compatible

The current handling for SRV resolution involves our own custom implementation of a DNS client. This client only reads DNS config from the linux /etc/resolv.conf folder, and I'm not actually certain that configuration is actually used by the DNS client itself? Additionally, the initialization of the DNS configuration is done solely through an atomic boolean, and is performed synchronously, and thus multiple concurrent calls to the function could lead to a race or blocked asio executor.