Implementing Fine Grids obstacle

Reference issue

Description

This merge request implements a new kind of obstacle for TELEMAC-2D: fine grids. The work and results of the implementation were presented during TUC 2025. A headloss based method was implemented (similar to what is done using user_dragfo routine) to account for fine grids. New keywords were added (2 integers, and 3 strings for new files). New routines were created : grid_headlosses.f, user_grid_headlosses.f, read_grd_data.f, lecgrd.f. Few routine modified, only for calls to the newly created ones (telemac2d, telemac2d_init, ...) New test case created and documentated with vnv script. User Guide for Telemac-2D was updated.

Checklist

All Merge Requests:

• Update NEWS.txt to describe your changes.
• Run build_telemac.py --check to check Fortran coding conventions.
• Run pylint to check Python coding conventions.
• Run build_telemac.py --rebuild for both Release and Debug configurations.
• Run validate_telemac.py for both Release and Debug builds.
• Run validate_telemac.py --notebook for both Release and Debug builds.
• Run doc_telemac.py if there are any modifications in the documentation.
• Run damocles.py --eficas if there are any modifications in the dictionaries.

In addition, for a new feature:

• Check that your feature works in both serial and parallel modes.
• Add at least one test case to check the functionality (with documentation, graphics and VnV script)
• Update the documentation for the module in which your feature will be available.