Reconsider the used method of thread-safety once updating to c-ares 1.23.0+

[czechboy0]

c-ares added opt-out thread-safety (simple locks around all channel-related functions) in 1.23.0: c-ares/c-ares#636

We're still using an older version, but once we update, we should either leave the c-ares provided lock in, and remove our outer lock in AresChannel.swift, or the opposite: disable c-ares locking, and keep ours. We want to avoid paying the cost for both.