Use memoryconservative mode for WF CSV_MERGE

[berland]

When run as a workflow job/ert plugin this has been observed through logging to fail due to lack of memory.

When run as a workflow job, it is probable that there is one CSV for every realization that is to be loaded, thus the memory conservative option probably makes sense to have on by default.

Keeping the faster option as default for usages as a forward model step.

[berland]

https://fmu-dashboard-fdeqekb8chekcqhu.neu.grafana.azure.com/d/ae0bpm0169ou8e/traces?from=1731324844410&to=1733916844410&var-operation_id=dbd6018074a3166d77e6c6c04d5dea03&orgId=1&viewPanel=2

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.15%. Comparing base (378bb74) to head (373ba36).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #765      +/-   ##
==========================================
- Coverage   85.17%   85.15%   -0.02%     
==========================================
  Files          52       52              
  Lines        7418     7418              
==========================================
- Hits         6318     6317       -1     
- Misses       1100     1101       +1     

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

[andreas-el]

I put my faith on you here.
Reasoning seems fair. 👍