Use encrypted dns proxy in `mullvad-ios` #471

Job	Run time
build-ios (aarch64-apple-ios)	1m 45s
clippy-check-ios (aarch64-apple-ios)	1m 22s
build-ios (aarch64-apple-ios-sim)	2m 23s
clippy-check-ios (aarch64-apple-ios-sim)	1m 22s
	6m 52s

Provide feedback