Add parameters related to reference oscillator to R&S ZNB driver

[mgunyho]

As the title says. Tested with a real device. Let me know if there is any issue with the formatting etc.

[mgunyho]

@microsoft-github-policy-service agree company="Aalto University"

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 10.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 67.29%. Comparing base (c5eedf9) to head (ff7e086). Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/qcodes/instrument_drivers/rohde_schwarz/ZNB.py	10.00%	9 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6352      +/-   ##
==========================================
- Coverage   67.30%   67.29%   -0.02%     
==========================================
  Files         352      352              
  Lines       32146    32156      +10     
==========================================
+ Hits        21637    21638       +1     
- Misses      10509    10518       +9     

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