Update snapshot testing dependency to 1.19.3

[Kyle-Ye]

Summary

• Update the Tuist and legacy Example projects to swift-snapshot-testing 1.19.3
• Refresh the checked-in package resolutions
• Align the legacy project's stale snapshot testing pin with its project requirement
• Update swift-custom-dump to the version required by SwiftPM trait resolution

Validation

• Resolved the Tuist package graph with SwiftPM
• Resolved the legacy Xcode project using its checked-in package versions
• Validated the legacy project file and package resolution files

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 13.77%. Comparing base (229647c) to head (060fc7e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #934      +/-   ##
==========================================
- Coverage   13.78%   13.77%   -0.01%     
==========================================
  Files         678      678              
  Lines       44500    44500              
==========================================
- Hits         6133     6130       -3     
- Misses      38367    38370       +3     

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