Hinted attribute validation

[GDYendell]

Breaking Changes

• Attempting to overwrite an Attribute now raises a RuntimeError, even if the type and access mode match. To statically type hint an Attribute to be introspected during initialisation, only specify the type hint on the class - do not create a default instance, e.g. attr: AttrRW[int], not attr = AttrRW(Int()).
• Controller.attributes is now a read-only view. Use Controller.add_attribute to create Attributes, which will perform validation.

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Sorry the diff is a bit horrible because I moved methods around, but I think it has made it easier to read through the code.

[codecov]

Codecov Report

❌ Patch coverage is 98.80952% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.35%. Comparing base (d750b61) to head (29c990a).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fastcs/controller.py	98.79%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #268      +/-   ##
==========================================
+ Coverage   89.33%   89.35%   +0.01%     
==========================================
  Files          45       45              
  Lines        2269     2273       +4     
==========================================
+ Hits         2027     2031       +4     
  Misses        242      242              

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