56 replace DeisaArray wrapper by Xarray

[JAuriac]

Close #56

[JAuriac]

We may want to consider "t" as an additional dimension rather than a metadata (which is how its handled currently)

[JAuriac]

The last commit moved "t" from a metadata (through "attrs") to a dimension (through "coords"), while adding complexity and inconsistencies of access, so we may want to rollback

attrs["t"] returns an int, it is simple and explicit
coords["t"] requires a .item() to extract an int, and access patterns are inconsistent (arr.coords["t"].item() or arr[-1].coords["t"] or arr.coords["t"][-1].item()) depending on whether the array has been indexed first

The following is a comparison :

def window_callback(window: list[xr.DataArray]):
    window[-1].attrs["t"]
    window[-1].data
def window_callback(window: list[xr.DataArray]):
    windowWithT = xr.concat(window, dim="t")
    windowWithT.coords['t'][-1].item()
    windowWithT[-1].data