add "from_pywasp_pwc" to XRSite

Following discussions of PyWAsP-PyWake coupling, we should add a XRSite class constructor from a pywasp Weibull wind climate (xr.Dataset) object.

A function to create a PyWake XRSite was added to pywasp here: https://gitlab-internal.windenergy.dtu.dk/ram/software/pywasp/pywasp/-/blob/209-add-aep-api-for-pywasp-to-allow-the-calcualte-of-aep-with-and-without-wakes-using-pywake/pywasp/wasp/aep.py#L179

However, we agreed it would be better to add a constructor in PyWake. The pywasp function can be deprecated/removed after it's added here.

Related to: https://gitlab-internal.windenergy.dtu.dk/ram/software/pywasp/pywasp/-/merge_requests/129 https://gitlab-internal.windenergy.dtu.dk/ram/software/pywasp/pywaspio/-/merge_requests/119