Sia Gupta

## Description Bringing RichTextBox style on parity with WinUI ## Regression None ## Testing Local build pass ## Risk NA ###### Microsoft Reviewers: [Open in CodeFlow](https://microsoft.github.io/open-pr/?codeflow=https://github.com/dotnet/wpf/pull/9550)

### Description This is a subissue to track the issues related to ComboBox apart from the ones mentioned in the parent issue #10393. Currently we have the following issues: -...