cleanup(netx): stop using most netxlite resolver internals (#797)

This diff modifies netx to stop using most netxlite resolver internals
but the internal function that creates a new, unwrapped system resolver,
which will be dealt with in a subsequent pull request.

See https://github.com/ooni/probe/issues/2121

internal/netxlite/legacy.go

@@ -9,16 +9,4 @@ package netxlite
 // Deprecated: do not use these names in new code.
 var (
 	NewResolverSystem = newResolverSystem
-	DefaultResolver   = newResolverSystem()
-)
-
-// These types export internal names to legacy ooni/probe-cli code.
-//
-// Deprecated: do not use these names in new code.
-type (
-	ErrorWrapperResolver           = resolverErrWrapper
-	ResolverSystemDoNotInstantiate = resolverSystem // instantiate => crash w/ nil transport
-	ResolverLogger                 = resolverLogger
-	ResolverIDNA                   = resolverIDNA
-	AddressResolver                = resolverShortCircuitIPAddr
 )