feat: move coordinate systems stub to grpc layer

[RobPasMue]

Moves the CoordinateSystemStub to the _grpc layer.

Some extra docstring fixes are performed

Related to #1817

[codecov]

Codecov Report

Attention: Patch coverage is 94.23077% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.37%. Comparing base (2d6153e) to head (3574f84).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...etry/core/_grpc/_services/v1/coordinate_systems.py	72.72%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1943   +/-   ##
=======================================
  Coverage   90.36%   90.37%           
=======================================
  Files         117      120    +3     
  Lines        9593     9634   +41     
=======================================
+ Hits         8669     8707   +38     
- Misses        924      927    +3     

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