Add convert_delft3d_to_sgrid

[erikvansebille]

Description

This PR adds a convert_delft3d_to_sgrid() function, to convert structured-grid netcdf output from Delft3D to SGrid, and use it in Parcels.

Note that the interpolation method is currently set to XFreeslip, which may not be the best choice for this data on a Grid. However, we can't use the CGrid_Velocity() interpolator as currently implemented in Parcels on the example data that I got from Port of Rotterdam), because the VELU and VELV velocities are rotated to the east and north directions - where the CGrid_Velocity() interpolator expects unrotated velocities in the M and N directions. I'm planning to talk to Deltares to see how we can fix this

Note that, at least for performance, this PR is blocked by #2780

Checklist

• Closes Reading Delft3D Flow NetCDF output into parcels #1205
• Tests added
• This PR targets the correct branch (main for normal development, v3-support for v3 support)

AI Disclosure

None

[VeckoTheGecko]

Small edit, but otherwise LGTM - I think this is a great starting point (and the warning is good to flag the degree of support we currently have)

[VeckoTheGecko]

-This tutorial shows how to load in files from the [Delft3D](https://www.deltares.nl/en/software/delft3d-4-suite/) model into Parcels. 
+This tutorial shows how to load in [Delft3D](https://www.deltares.nl/en/software/delft3d-4-suite/) model output files (in NetCDF format) into Parcels.

if I recall correctly, NetCDF wasn't the default output format for Delft3D. Best to be explicit here I think

[erikvansebille]

Thanks! The default output for Delft3D is netcdf (it isn't for SWASH; see #2764). But your suggestion is good anyways