[wnbd-build] Add Jenkins job to build the wnbd project

[wnbd-build] Add Jenkins job to build the wnbd project

* Add the Jenkins job used to build the `wnbd` project.
* Add the following utils functions: `ssh_exec`, `scp_upload`, `scp_download`.
* Add `./scripts/ceph-windows/cleanup` script that can be used as a
  post-build step to clean up the Windows test / build environment.
* Add `./scripts/ceph-windows/setup_libvirt_vm` script used to spawn a
  libvirt VM with the Windows test / build environment.
* Upload the build artifact to chacra.