Create a plain test recipe for remote linux connectivity related issues

In order to avoid regressions when touching linuxdevice.cpp it would be good to have a list of recipes (e.g. as plain text in some tests/manual/remotelinux/testplan.txt) to cover the typical workflows and expectations when setting up remote linux devices, similar to what was mentioned in https://codereview.qt-project.org/c/qt-creator/qt-creator/+/601906:

• Have a valid device.
• Change e.g. its IP address to something invalid.
• Do not re-test.
• Try to deploy a remote application, which will fail.
• The device should afterwards get marked as disconnected (complete with info popup).

For now, just a description