Private builds and tests

[aliceinwire]

As wrote in the #2594 feature request and in a similar way that KCIDB is allowing for private results kernelci/kcidb#326.
Would be nice to have a feature added to kci tool command that request for private build and test on the production or local KernelCI server.
One way of doing this could be to have a device set to private by permissions on the lava server and send private requests from the kci tool

[aliceinwire]

from KernelCI weekly discussion KernelCI cannot guarantee privacy but still would be helpful for development reasons to have the possibility to choose whether to don't publish results on KernelCI dashboard or KCIDB