editor: Add support for no scroll margin in full mode (#41838)

Noticed this whilst testing the Docker debugger. I randomly scrolled the
console off screen and was confused briefly as to why this was the case.

Release Notes:

- The debugger query console will no longer needlessly overscroll.

crates/editor/src/editor_tests.rs

@@ -14217,7 +14217,7 @@ async fn test_completion_in_multibuffer_with_replace_range(cx: &mut TestAppConte
                     EditorMode::Full {
                         scale_ui_elements_with_buffer_font_size: false,
                         show_active_line_background: false,
-                        sized_by_content: false,
+                        sizing_behavior: SizingBehavior::Default,
                     },
                     multi_buffer.clone(),
                     Some(project.clone()),