Add param to enable four-wire measurement on Keithley 2600 driver.

[trlemon]

Added parameter for enabling four-probe measurement on Keithley 2600.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.54%. Comparing base (115339f) to head (2a22981).
⚠️ Report is 21 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7942   +/-   ##
=======================================
  Coverage   60.54%   60.54%           
=======================================
  Files         333      333           
  Lines       32230    32232    +2     
=======================================
+ Hits        19514    19516    +2     
  Misses      12716    12716           

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