Room: emit addedMessages() before possible read marker auto-promotion
Room: emit addedMessages() before possible read marker auto-promotion

Read marker auto-promotion may be bound to a dataChanged() signal in the
client model, while a routine connection for addedMessages() is
endInsertRows(). Emitting endInsertRows() after dataChanged() over the
same rows has unpredictable consequences for representation of data in
those rows - hence the fix.

QMatrixClient/libqmatrixclient,Fxrh/libqmatrixclient,QMatrixClient/libqmatrixclient