Replace ProxyInfo constructor with public API

ProxyInfo is inculded in connectivity mainline module
so the dependencies on hidden API needs to be removed.

Bug: 178777253
Test: build ManagedProvisioning pass
      ManagedProvisioningTests:WifiConfigurationProviderTest
Change-Id: I9e3b4269bfd204c7caede2f4bb92f65d26f1cd26
1 file changed