Add Ceph Windows testing job

Add Ceph Windows testing job

Add a new freestyle Jenkins job that can be used to test a Ceph
Windows build uploaded to Chacra, on the Jenkins agents labeled with
`amd64`, `focal`, `libvirt`.

The Ceph Windows build is identified in Chacra using the following
Jenkins job parameters:
* `CEPH_WINDOWS_VERSION`
* `CEPH_WINDOWS_SHA1`

As a build step, the new job will execute the `./build/run_tests`
bash script. This script sets up a KVM virtual machine with Windows
Server 2019, that it's used to run the Ceph Windows unit tests from
the Chacra build. On top of that, it takes care of the everything
needed to run the Ceph Windows tests.