[QGIS-Developer] Retrieve folder path from Processing scripts

[matteo]

Hi devs,

fighting with this problem I might have found a small bug (if someone
can confirm this).

So with `QgsProcessingParameterFolderDestination` and
`parameterAsString` Processing takes the path only if the path is added
manually OR if the user choose the path from the button BUT types
something in the box.

If the path is taken directly from the button I always get a temporary path

If someone wants to give a try I have prepared a copy/paste script for
testing here:

https://pastebin.com/DEHvD0nr

If confirmed I can open a ticket

Thanks

Matteo