fix: Respect AllowNullPropertyAssignment correctly when mapping code is not a direct assignment

[latonz]

Respect AllowNullPropertyAssignment correctly when mapping code is not a direct assignment

Description

If AllowNullPropertyAssignment is true, respect it correctly (set target members to null) if the mapping for the property is not accepting null values and is not synthetic.

This could have a big impact, we should probably release this as breaking change 🤔
Fixes #803

Checklist

• The existing code style is followed
• The commit message follows our guidelines
• Performed a self-review of my code
• Hard-to-understand areas of my code are commented
• The documentation is updated (as applicable)
• Unit tests are added/updated
• Integration tests are added/updated (as applicable, especially if feature/bug depends on roslyn or framework version in use)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (825a853) 91.23% compared to head (8d28c9c) 91.24%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #939      +/-   ##
==========================================
+ Coverage   91.23%   91.24%   +0.01%     
==========================================
  Files         222      222              
  Lines        7085     7097      +12     
  Branches      895      897       +2     
==========================================
+ Hits         6464     6476      +12     
  Misses        411      411              
  Partials      210      210              

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[github-actions]

🎉 This PR is included in version 3.3.0-next.5 🎉

The release is available on:

• GitHub release
• v3.3.0-next.5

Your semantic-release bot 📦🚀

[github-actions]

🎉 This PR is included in version 3.3.0 🎉

The release is available on:

• GitHub release
• v3.3.0

Your semantic-release bot 📦🚀