Move ContentSize requirements from Node to the widget defining components (#16083)

# Objective

Missed this in the required components PR review. `ContentSize` isn't
used by regular UI nodes, only those with intrinsically sized content
that needs a measure func.

## Solution

Remove `ContentSize` from `Node`'s required components and add it to the
required components of `Text` and `UiImage`.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

Author: ickshonpe

crates/bevy_ui/src/ui_node.rs

@@ -1,4 +1,4 @@
-use crate::{ContentSize, FocusPolicy, UiRect, Val};
+use crate::{FocusPolicy, UiRect, Val};
 use bevy_color::Color;
 use bevy_ecs::{prelude::*, system::SystemParam};
 use bevy_math::{vec4, Rect, Vec2, Vec4Swizzles};
@@ -286,7 +286,6 @@ impl From<&Vec2> for ScrollPosition {
     BackgroundColor,
     BorderColor,
     BorderRadius,
-    ContentSize,
     FocusPolicy,
     ScrollPosition,
     Transform,

crates/bevy_ui/src/widget/text.rs

@@ -102,7 +102,7 @@ pub struct TextBundle {}
 /// ```
 #[derive(Component, Debug, Default, Clone, Deref, DerefMut, Reflect)]
 #[reflect(Component, Default, Debug)]
-#[require(Node, TextLayout, TextFont, TextColor, TextNodeFlags)]
+#[require(Node, TextLayout, TextFont, TextColor, TextNodeFlags, ContentSize)]
 pub struct Text(pub String);
 
 impl Text {