Always inherit from base class (don't squash) when oneOf ref'd via discriminator

[pettijohn]

Resolves #5014

[pettijohn]

@microsoft-github-policy-service agree

[andrueastman]

This looks good to me. Validated generation with microsoftgraph/msgraph-sdk-dotnet#2615

@pettijohn Any chance you can add an entry to the Changelo file at the repository root as well?

[baywet]

Thanks for the contribution!
I did a little bit of cleanup for unused parameters.

[pettijohn]

Thank you! Looks like @baywet added the changelog entry.