fix(Keithley3706A): Fix interlock status dictionary

[brandonaltieri1]

When instantiating an object of the class Keithley3706A, the interlock status is checked for each card that is installed in the unit. When querying the unit for the interlock status (for a specific slot), the unit can return any of the following values:

See page 742 of https://download.tek.com/manual/3700AS-901-01D_Jul_2018_Ref_0.pdf. The interlock state is mapped using a dictionary (interlock_status in the get_interlock_state method), where the returned value is used as the key to find the appropriate status string. However, this dictionary was initially defined using only two keys, 0 and 1. When querying the interlock status, the possible return values are nil, 0, 1, 2, and 3. As some of these return values are not included as keys in the interlock_status dictionary, when the unit does not return 0 or 1, a KeyError is raised, and the driver cannot be instantiated. This PR updates this interlock_status dictionary to include all possible return values as keys, and adds the associated status strings (taken directly from the reference manual). The unit test/sim file are both updated to reflect these changes.

[codecov]

Codecov Report

Merging #5013 (1340484) into master (73c352f) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5013      +/-   ##
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- Coverage   67.22%   67.19%   -0.04%     
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  Files         356      356              
  Lines       29726    29729       +3     
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- Hits        19984    19977       -7     
- Misses       9742     9752      +10     

[jenshnielsen]

Thanks @brandonaltieri1 could you add a short message to a file called 5013.improved_driver in docs\changes\newsfragments explaining the fix

[brandonaltieri1]

Thanks @brandonaltieri1 could you add a short message to a file called 5013.improved_driver in docs\changes\newsfragments explaining the fix

Done, thanks @jenshnielsen!