Consider removing default mesh type from Grid class

[erikvansebille]

As reported in #2406, things can go pretty wrong when the Grid assumes a "flat" mesh instead of a "spherical" one (or vice versa).

The default for XGrid is now "flat":

Parcels/src/parcels/_core/xgrid.py

Line 105 in 0d419a2

def __init__(self, grid: xgcm.Grid, mesh="flat"):

And so is the default for UxGrid:

Parcels/src/parcels/_core/uxgrid.py

Line 21 in 0d419a2

def __init__(self, grid: ux.grid.Grid, z: ux.UxDataArray, mesh="flat") -> UxGrid:

Perhaps it's better to remove this default and let the user be explicit about it? Of course, FieldSet.from_* methods could use the appropriate mesh_type so most users won't notice.

@VeckoTheGecko, what do you think?

And @fluidnumerics-joe, do you think removing the default mesh would also make sense for uxgrid?

[VeckoTheGecko]

yes, I think this makes sense

[erikvansebille]

Fixed in #2411