Refactor Keithley drivers

[jenshnielsen]

Convert all Keithley drivers to new add_parameter format.
Don't document inherited attributes
Document base classes
A fix docs fixes

TODO

• News fragment

[codecov]

Codecov Report

Attention: Patch coverage is 71.94245% with 78 lines in your changes are missing coverage. Please review.

Project coverage is 67.65%. Comparing base (10785d5) to head (00934db).
Report is 9 commits behind head on main.

Files	Patch %	Lines
...codes/instrument_drivers/Keithley/Keithley_2000.py	0.00%	30 Missing ⚠️
...codes/instrument_drivers/Keithley/Keithley_2400.py	0.00%	24 Missing ⚠️
...codes/instrument_drivers/Keithley/Keithley_6500.py	0.00%	24 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6115      +/-   ##
==========================================
+ Coverage   67.63%   67.65%   +0.02%     
==========================================
  Files         352      352              
  Lines       30746    30886     +140     
==========================================
+ Hits        20795    20896     +101     
- Misses       9951     9990      +39     

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