Avoid cloning Rows during Galley::concat (#7649)

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Moves `ends_with_newline` into `PlacedRow` to avoid clones during
layout.
I don't think there was a rationale stronger than "don't change too
much" for not doing this in https://github.com/emilk/egui/pull/5411, so
I should've just done this from the start.
This was a significant part of the profile for text layout (as it cloned
almost every `Row`, even though it only needed to change a single
boolean).

Before:
<img width="757" height="250" alt="image"
src="https://github.com/user-attachments/assets/d1c2afd1-f1ec-4cf5-9d05-f5a5a78052df"
/>

After:
<img width="615" height="249" alt="image"
src="https://github.com/user-attachments/assets/c70966da-c892-4e84-adba-494d0f37f263"
/>

(note that these profiles focus solely on the top-level
`Galley::layout_inline` subtree, also don't compare sample count as the
duration of these tests was completely arbitrary)

egui_demo_lib `*text_layout*` benches:
<img width="791" height="461" alt="image"
src="https://github.com/user-attachments/assets/4f97ce84-2768-4876-9488-d42f8f358ed1"
/>

* [X] I have followed the instructions in the PR template

(As usual, the tests fail for me even on master but the failures on
master and with these changes seem the same :))

crates/epaint/src/shapes/text_shape.rs

@@ -137,7 +137,12 @@ impl TextShape {
         *mesh_bounds = transform.scaling * *mesh_bounds;
         *intrinsic_size = transform.scaling * *intrinsic_size;
 
-        for text::PlacedRow { pos, row } in rows {
+        for text::PlacedRow {
+            pos,
+            row,
+            ends_with_newline: _,
+        } in rows
+        {
             *pos *= transform.scaling;
 
             let text::Row {
@@ -145,7 +150,6 @@ impl TextShape {
                 glyphs: _, // TODO(emilk): would it make sense to transform these?
                 size,
                 visuals,
-                ends_with_newline: _,
             } = Arc::make_mut(row);
 
             *size *= transform.scaling;