[ui] fix: Adding a node, with an expression on a 3d output file, the eye icon should be visible

[nicolas-lambert-tc]

Description

A signal is missing on attribute, to notify the parent's node that an expression has been applied.
You can test it by adds a convertMesh node into any graph. It should have an eye visible.

Implementation remarks

This PR add this signal expressionApplied ans emit it just after an expression has been applied on the attribute.
The node eye visiblity was listening to the outputAttrEnabledChanged.
It has been renamed to in this PR in order to outputAttrChanged because now it reacts to the expressionApplied and the attributeEnabled signals.

Features list

• Fix Node-eye not visible even if an output 3d file exists in the node.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.87%. Comparing base (cff6ac5) to head (f766b31).
⚠️ Report is 6 commits behind head on develop.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
meshroom/core/node.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2929   +/-   ##
========================================
  Coverage    80.86%   80.87%           
========================================
  Files           57       57           
  Lines         7792     7796    +4     
========================================
+ Hits          6301     6305    +4     
  Misses        1491     1491           

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