Sort Cached Messages

Summary: Previously, incoming messages were appened to a QList. This list was accidentally sorted because that's how Android returned them, but new messages were appended to the wrong end of the list. This patch specifically and intentionally sorts messages so new ones become visible

Test Plan:

• Open SMS GUI, verify that the most-recent messages are shown
• Either send or recieve an SMS
• Wait about 5s (I do not know why this is necessary. Probably some Android weirdness)
• De-select the current conversation, then re-select it
  • TODO: Make the app automatically respond to new messages
• The newly sent or recieved message should be shown in the most-recent position

Reviewers: apol

Reviewed By: apol

Subscribers: apol, nicolasfella, kdeconnect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D15108