Vertical text support for TextBox/TextBlock/RichTextBox

Japanese can be written from [top-to-bottom, right-to-left](https://en.wikipedia.org/wiki/Japanese_language_and_computers#Direction_of_text). I would like to be able to present texts in this format in my WPF projects. Petty tricks like rotating the control won't give the [desired result](https://www.w3.org/International/articles/vertical-text/index).

Suggestion:
Add a new [FlowDirection](https://learn.microsoft.com/en-us/dotnet/api/system.windows.flowdirection) enum like "VerticalRightToLeft" that allows the aforementioned behavior.

Start by reading the existing FlowDirection API and the TextBox, TextBlock, and RichTextBox entry points named in the issue, then determine how their layout and text direction are currently handled. Done means these controls support Japanese top-to-bottom, right-to-left text through a defined FlowDirection value without relying on rotation.

Written by the indexing model from the issue text.