Make command caller get/set_raw a method

[jenshnielsen]

This makes get/set_raw proper methods rather than callable attributes and furthermore extracts the logic of generating the get/set_raw code into a factory function for added clarity.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.49123% with 2 lines in your changes missing coverage. Please review.

Project coverage is 67.22%. Comparing base (e7dd669) to head (dc159ac). Report is 2 commits behind head on main.

Files	Patch %	Lines
src/qcodes/parameters/parameter.py	96.49%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5724      +/-   ##
==========================================
+ Coverage   67.19%   67.22%   +0.02%     
==========================================
  Files         352      352              
  Lines       32154    32184      +30     
==========================================
+ Hits        21607    21635      +28     
- Misses      10547    10549       +2     

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