Handle server certificate update if user is already logged in

In case of not trusted SSL certificate, RiotX show a dialog during login steps to let the user trust it if he wants to. But if certificate change server side after the login, RiotX will get stucked.

There are already some TODOs in the code to handle properly this use case.

To test: login to a homeserver with a trusted certificate (such as matrix.org for instance). Then set https://github.com/vector-im/riotX-android/blob/b8b79de91c62d8748a319d1621067a1f930d369a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/network/ssl/PinnedTrustManagerProvider.kt#L25 to false and deploy again the app.

FTR: issue (fixed) on Riot-Android: https://github.com/vector-im/riot-android/issues/1592