Replace fallback urls for captive portal check

• /e/ version: Pie, Oreo, Nougat
• Device model:
• Reproducible with the last /e/ version: yes
• Reproducible with LineageOS: -

Summary

The main URLs for captive portal checking already point to domains from /e/. However, fallback URLs still point to Google. This should be replaced with safer values also pointing to /e/ or any other privacy-respecting service.

This improvement concerns

• UI
• Behavior
• Privacy

Description

What is the current behavior?

Fallback URLs for captive portal checking still point to Google servers in Pie, Oreo and Nougat branches. Pie: https://gitlab.e.foundation/e/os/android_frameworks_base/-/blob/v1-pie/services/core/java/com/android/server/connectivity/NetworkMonitor.java#L108

Oreo: https://gitlab.e.foundation/e/os/android_frameworks_base/-/blob/v1-oreo/services/core/java/com/android/server/connectivity/NetworkMonitor.java#L98

Nougat: https://gitlab.e.foundation/e/os/android_frameworks_base/-/blob/v1-nougat/services/core/java/com/android/server/connectivity/NetworkMonitor.java#L92

What is the improved behavior?

The default config values should be replaced with domains from /e/ or other privacy-respecting services. E.g. https://connectivity.ecloud.global or http://204.ecloud.global

To not undermine the purpose of fallback URLs, maybe use other hosts than for the default URLs.

What does it bring?

Improves privacy if captive portal check on ecloud.global fails.