Add StructuredMeshView to fluxes.

[SimonCan]

Added StructuredMeshView{2} to various flux functions to fix issue with some coupled simulations.

[github-actions]

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[sloede]

LGTM. Please run formatter, mark as ready for review, and re-request review 😊

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.19%. Comparing base (58acd35) to head (cb775a0).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1986   +/-   ##
=======================================
  Coverage   96.19%   96.19%           
=======================================
  Files         460      460           
  Lines       36993    36993           
=======================================
  Hits        35584    35584           
  Misses       1409     1409           

Flag	Coverage Δ
unittests	96.19% <100.00%> (ø)

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[SimonCan]

LGTM. Please run formatter, mark as ready for review, and re-request review 😊

Thanks. Just applied it.