[csharp][default] Fix handling of nested inheritance properties

Created by: Blackclaws

This addresses #8849 partly as there is still another bug remaining. However this addresses the handling of nested inheritance which fixes the model classes created. It contains a change to the default codegen code as well as the issue was actually partly rooted much deeper.

Following issues were fixed:

• Adding properties defined on a composed schema to the inheriting child in a chain inheritance setting
• Fixing csharp codegens when the components had names with underscores in them when inheritance is involved

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
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  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh

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