ceph-windows: Update `ceph-windows-test` Jenkins job

ceph-windows: Update `ceph-windows-test` Jenkins job

Make the Jenkins `ceph-windows-test` similar to `ceph-windows-pull-requests` job.

However, `ceph-windows-test` is meant to be triggered on-demand, and it
exposes more parameters for `win32_build.sh` script, and artifacts collected
at the end of the job run.

The new `ceph-windows-test` Jenkins job will have the following new parameters:

* `CEPH_GIT_REPO` - The Ceph git repo used to clone.
* `CEPH_GIT_BRANCH` - The Ceph git branch name used to clone.
* `CEPH_WIN32_BUILD_FLAGS` - Build flags passed to `win32_build.sh`
   besides the defaults.
* `INCLUDE_USERSPACE_CRASH_DUMPS` - Collect Windows userspace crash dumps
   with the job artifacts.
* `INCLUDE_CEPH_ZIP` - Collect the `ceph.zip` Windows build with the
   job artifacts. This is useful for debugging failures locally.

Also, create `scripts/ceph-windows/win32_build` common script. This is
used in both Jenkins jobs to cross-build Ceph Windows.

Besides this, we collect artifacts with `trap EXIT` instance.
Previously, if the tests failed, the artifacts wouldn't be collected.

Due to the fact that artifacts collected might occupy more space,
we limit `artifact-num-to-keep` to `15`.

Signed-off-by: Ionut Balutoiu <ibalutoiu@cloudbasesolutions.com>