Proposal: Explicit LTR/RTL TextReadingOrder

### Title

Add `LeftToRight` and `RightToLeft` values to `TextReadingOrder` enum which explicitly set the reading order without using the content or the `FlowDirection`.

### Summary

Developers should be able to explicitly set the `TextReadingOrder` to either `LeftToRight` or `RightToLeft` rather than ensuring `TextReadingOrder="UseFlowDireciton"` and assigning the `FlowDirection`.

### Rationale

This allows developers to more easily control the text reading order of text through direct control rather than tangentially by adjusting multiple properties.

### Scope

| Capability | Priority |
| :---------- | :------- |
| This proposal will allow developers to explicitly set the `TextReadingOrder` | Must |
| This proposal will allow end users to read text in their language more easily | Must |

### Important Notes

Notice the period by the arrow is on the other side of the message than all the others.

That is because the string begins with a formatted token, and the `TextReadingOrder` is `DetectFromContent`. The text flow direction is detected as left to right because the first directional character in the string is `'s'`. That's perfectly expected but, in this instance, incorrect. I believe the developer should be able to explicitly set the `TextReadingOrder` to either `LeftToRight` or `RightToLeft` without setting the `FlowDirection`, since that would invert all the other properties (such as alignment).

The image below shows what happens if you set **ONLY** the `FlowDirection` to `RightToLeft` and `TextReadingOrder` to `UseFlowDirection`.

The text reading order is fixed! But notice how the `TextAlignment` is inverted as well. In order to restore left hand alignment, you must also set the `TextAlignment` to `Right`. However, you must **not** invert the `TextAlignment` if the app `FlowDirection` is the same as the text flow direction. I would consider this a work-around. Not a fix.

As is, RTL localization is often overlooked, and this a small convenience that can greatly simplify displaying RTL text in an LTR environment or vice-versa.

### Open Questions

_No response_

Start by locating the TextReadingOrder enum and the code handling DetectFromContent and UseFlowDirection. Review how reading order and FlowDirection currently affect alignment; the work is done when LeftToRight and RightToLeft explicitly control text reading order without requiring or changing FlowDirection.

Written by the indexing model from the issue text.