fix: single phase statistics CSV generation

[arng40]

Missing "," in csv headers and average/min pressure have been reversed

[MelReyCG]

Uniformize with the compositionalMultiphaseStatistics.cpp:

• use a TableLayout in the rows output
• Also, if it is not too much out of scope, you can keep the formatter as a private member (preventing any different parameter count in the CSV header & data)

[MelReyCG]

You can ignore my previous comment as I am doing it in #3826

[codecov]

Codecov Report

❌ Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.87%. Comparing base (2acb3ef) to head (620de53).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
...physicsSolvers/fluidFlow/SinglePhaseStatistics.cpp	0.00%	14 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3928      +/-   ##
===========================================
- Coverage    58.87%   58.87%   -0.01%     
===========================================
  Files         1353     1353              
  Lines       112953   112955       +2     
===========================================
  Hits         66504    66504              
- Misses       46449    46451       +2     

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