Private builds and tests

As wrote in the https://github.com/kernelci/kernelci-core/issues/2594 feature request and in a similar way that KCIDB is allowing for private results https://github.com/kernelci/kcidb/issues/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`

Start by reading feature request #2594 and the related KCIDB issue #326, then trace the `kci tool` command and how it sends requests to production or local KernelCI servers. Check how device permissions are configured on the LAVA server. Done means private build and test requests can be requested through the CLI and handled for both server contexts.

Written by the indexing model from the issue text.