[femutils] Remove usage of CsrFormatMatrixView:rowsNbColumn()

[grospelliergilles]

This is the first step needed to remove the array containing this value.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.52%. Comparing base (1929507) to head (19c585d).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #350      +/-   ##
==========================================
+ Coverage   69.50%   69.52%   +0.02%     
==========================================
  Files         118      118              
  Lines       14704    14704              
  Branches     1983     1983              
==========================================
+ Hits        10220    10223       +3     
+ Misses       4028     4025       -3     
  Partials      456      456              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.