Add IpConfiguration parcelable interface implementation to system API

API lint robot warnings that parcelable requires writeToParcel
and describeContents.

Bug: 139268426
Bug: 135998869
Test: atest android.net.cts
      atest android.net.wifi.cts
      atest FrameworksNetTests
      ./frameworks/opt/net/wifi/tests/wifitests/runtests.sh

Change-Id: I7acf000c468788c3fdcb47f8601762e7804ab940