Use a different icon for eased keyframes in the animation editor

This makes easing tracks easier to recognize, in a way similar
to curved lines in the Path2D editor.

editor/animation_track_editor.cpp

@@ -2257,6 +2257,11 @@ void AnimationTrackEdit::draw_key(int p_index, float p_pixels_sec, int p_x, bool
 
 	Ref<Texture2D> icon_to_draw = p_selected ? selected_icon : type_icon;
 
+	if (animation->track_get_type(track) == Animation::TYPE_VALUE && !Math::is_equal_approx(animation->track_get_key_transition(track, p_index), real_t(1.0))) {
+		// Use a different icon for keys with non-linear easing.
+		icon_to_draw = get_theme_icon(p_selected ? SNAME("KeyEasedSelected") : SNAME("KeyValueEased"), SNAME("EditorIcons"));
+	}
+
 	// Override type icon for invalid value keys, unless selected.
 	if (!p_selected && animation->track_get_type(track) == Animation::TYPE_VALUE) {
 		const Variant &v = animation->track_get_key_value(track, p_index);

editor/icons/KeyEasedSelected.svg

@@ -0,0 +1 @@
+<svg height="10" viewBox="0 0 10 10" width="10" xmlns="http://www.w3.org/2000/svg"><rect fill="#5fb2ff" height="9.999999" rx=".948002" stroke-width="1.2427" width="9.999999" x=".000001" y=".000035"/><rect fill="#003e7a" height="5.628136" rx=".533549" stroke-width=".699406" transform="matrix(.99989481 .01450427 .01450427 .99989481 0 0)" width="5.628136" x="2.115027" y="2.114924"/></svg>

editor/icons/KeyValueEased.svg

@@ -0,0 +1 @@
+<svg height="10" viewBox="0 0 10 10" width="10" xmlns="http://www.w3.org/2000/svg"><rect fill="#e0e0e0" height="8.000001" rx="1.000032" ry="1.00003" stroke-width="1.3109" transform="rotate(-90)" width="8.000016" x="-9.000016" y=".999999"/></svg>