InProcessNetworkStack requires platform-signed APK

PlatformCaptivePortalLogin must be used with InProcessNetworkStack
instead of CaptivePortalLogin, since the signature of the APKs must
match.

Bug: 132666298
Test: Flashed walleye_svelte-eng, networking and captive portal working,
      including "use as-is".

Change-Id: I243b29f2397b22f0d55af0d8927e75916d644198