Misleading namings in `bevy_text`

## Problem

The names of some of the components in `bevy_text` are confusing and inconsistent:

* `TextLayoutInfo`
Contains the final computed text layout. The `-Info` suffix is redundant and potentially confusing.

* `TextLayout`
Holds the settings for text justification and line breaking. Not the layout.

* `ComputedTextBlock`
This holds the cosmic-text buffer. The name suggests that it contains the final result of a text relayout, but the buffer can be out-of-date until it is updated during the text schedule.

## Suggestions

Renamings:
* `TextLayoutInfo` -> `ComputedTextLayout`
* `ComputedTextBlock` -> `TextBuffer`

Remove the `TextLayout` component.

`JustifyText` and `LineBreak` become components `Require`d by `Text` and `Text2d`.

Start in the `bevy_text` module and trace references to `TextLayoutInfo`, `TextLayout`, `ComputedTextBlock`, `JustifyText`, and `LineBreak`. The work is complete when the proposed renamings and component removal are applied consistently, with `JustifyText` and `LineBreak` required by `Text` and `Text2d`.

Written by the indexing model from the issue text.