Draft: Generalize field declaration for the LSQ reconstruction routines

What is the new feature

The field declaration of the LSQ reconstruction routines has been slightly generalized, in order to make the routines applicable to the ocean surface wave model ICON-wave.

How is it implemented

Currently, the 'vertical' or '3rd' dimension of the local field z_b is implicitly identified with p_patch%nlev. This is fine for the atmosphere model, but does not work for ICON-WAVE, where the 3rd dimension is the total number of spectral wave energy bins. This issue has been solved by replacing

REAL(wp) :: z_d(3, nproma, nlev)

with

REAL(wp) :: z_d(3, nproma, elev)

As a side effect, nlev is no longer needed by the reconstruction routines. The argument lists have been adapted accordingly.

@m222072

Mandatory steps before review

• Gitlab CI passes (Hint: use make format for linting)
• New feature is covered by additional unit tests
• Mark the merge request as ready by removing Draft:

Mandatory steps before merge

• Reviewed by a maintainer
• Incorporate review suggestions
• Remember to edit the commit message and select the proper changelog category (feature/bugfix/other)
• Prior to merging, please remove any boilerplate from the MR description, retaining only the Please describe your feature in a couple of words and describe important implementation details of the feature section to maintain

You are not supposed to merge this request by yourself, the maintainers of libiconmath take care of this action!