fix: Proxy model not setting defined values in parent class

[mattrunyon]

Something I noticed when working on dh.ui databars. I don't think this currently causes any issues in DHC, but it could. If we defined a member field in the proxy model and then set the value, we could end up with the wrong values.

This is only an issue if we directly set a public member. In the current proxy model, we only set via setField type functions, so things seem to be fine. Inside of class definitions the proxy is skipped (since the proxy is just returned from the ctor).

This change makes setting a member defined in the proxy class work even if you try to do it on the proxy object.

class ProxyModel {
  myField = 4
}

test = new ProxyModel();
test.myField; // 4
test.model.myField; // undefined

test.myField = 5;
test.myField; // 4 - WRONG
test.model.myField; // 5

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.67%. Comparing base (a257296) to head (cb7cb26).

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #2187    +/-   ##
========================================
  Coverage   46.66%   46.67%            
========================================
  Files         692      692            
  Lines       38629    38630     +1     
  Branches     9814     9630   -184     
========================================
+ Hits        18028    18029     +1     
- Misses      20548    20590    +42     
+ Partials       53       11    -42     

Flag	Coverage Δ
unit	46.67% <100.00%> (+<0.01%)	⬆️

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