## Summary
This patch adds an interface to return only a specified window of messages, making loading the conversations history smooth, fast, and enjoyable.

The current implementation of the conversation interface loads all messages every time the conversation is requested. This is might be painfully slow to load in case the conversation is large or if there are a lot of MMS/RCS messages in the conversation (since those are wildly slower to load than SMS)

Requires https://invent.kde.org/kde/kdeconnect-android/merge_requests/122 to enable Android functionality

## Test Plan

 - With new Android app and old Desktop app:
   - The Android app will notice the missing fields and query for all messages as before.
 - With old Android app and new Desktop app:
   - The desktop will send fields for the new interface which will not be read and all messages will be returned.
 - With new Android app and new Desktop app:
   - The new interface is used and returns only a certain number of messages at a time.