Provide a custom exception message to Timeout.timeout calls

The driver has two places where it calls Timeout.timeout:

lib/mongo/socket/ssl.rb: Timeout.timeout(connect_timeout, Error::SocketTimeoutError) do
lib/mongo/socket/tcp.rb: Timeout.timeout(connect_timeout, Error::SocketTimeoutError) do

These calls specify a custom exception class but not a custom message. We can additionally supply a custom message to make it more clear when troubleshooting whether a timeout is driver-originated or comes from someone wrapping a call (possibly via patching the driver) in Timeout.timeout.