Cloud project transfer dialog bug hunting and improvements

[nirvn]

This mainly started with fixing something that's been a problem with QFieldSync for a long while and negatively impacts the process of uploading projects to QFieldCloud: the feedback table widget shown when layer(s) or the project being uploaded has issues will often appear twice.

Here's an example:

The table is already scary, we just end up scaring people twice as much due to this glitch ;)

While looking into this dialog, I then took the time to improve the vertical spread of widgets there. ATM, none of the widgets expand, leaving empty spaces all around:

By having the feedback table expand to fill all available space, we end up with a much nicer dialog.

Finally, I've removed the use of ALL CAPS for the warning and error label, added nice icons (to better match the feedback dialog QGIS has within the layout designer), and I've merged the source + message columns to better manage the space we have.

The final look: