Label does not respect `LayoutJob` alignment when using `add_sized`

Nobody has claimed this yet.

**Describe the bug**

What I'm trying to accomplish is aligning some text left, and some text right within a container.

The method I'm using is:
* Container with `Layout::right_to_left`.
* Adding the right-most label first.
* Adding the left-most label second using `add_sized` and the available size.

This almost works, but the text inside the left-most label is centered instead of left-aligned.

**To Reproduce**

```rust
ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
let left = egui::text::LayoutJob::default();
egui::RichText::new("left").color(egui::Color32::WHITE).append_to(
&mut left,
&text_style,
egui::FontSelection::default(),
egui::Align::Min,
);
let right = egui::text::LayoutJob::default();
egui::RichText::new("right").color(egui::Color32::WHITE).append_to(
&mut right,
&text_style,
egui::FontSelection::default(),
egui::Align::Min,
);
ui.add(egui::Label::new(right));
ui.add_sized(ui.available_size(), egui::Label::new(left));
});
```

**Expected behavior**

Text within the `Label` is left aligned since it is specified in `RichText` (`egui::Align::Min`).

Maybe there is some other way to achieve what I'm trying to do?

Start with the Rust reproduction using Label, LayoutJob, add_sized, and Layout::right_to_left. Investigate how the label's available size is combined with the alignment specified in RichText. Done means the left label's text is left-aligned while the right label remains right-aligned in the shown layout.

Written by the indexing model from the issue text.