Improve folding appearance in the editor inspector

The arrow is now displayed at the left to be consistent with
other places where folding is used. The arrow icons used are now
consistent with the rest of the editor. The `arrow_up` icon is
no longer used anywhere, so it was removed.

Additional spacing was also added for a better visual appearance.

editor/editor_inspector.cpp

@@ -1046,9 +1046,9 @@ void EditorInspectorSection::_notification(int p_what) {
 
 		if (foldable) {
 			if (object->editor_is_section_unfolded(section)) {
-				arrow = get_icon("arrow_up", "Tree");
-			} else {
 				arrow = get_icon("arrow", "Tree");
+			} else {
+				arrow = get_icon("arrow_collapsed", "Tree");
 			}
 		}
 
@@ -1087,9 +1087,9 @@ void EditorInspectorSection::_notification(int p_what) {
 
 		if (foldable) {
 			if (object->editor_is_section_unfolded(section)) {
-				arrow = get_icon("arrow_up", "Tree");
-			} else {
 				arrow = get_icon("arrow", "Tree");
+			} else {
+				arrow = get_icon("arrow_collapsed", "Tree");
 			}
 		}
 
@@ -1103,13 +1103,12 @@ void EditorInspectorSection::_notification(int p_what) {
 
 		draw_rect(Rect2(Vector2(), Vector2(get_size().width, h)), bg_color);
 
-		int hs = get_constant("hseparation", "Tree");
-
+		const int arrow_margin = 3;
 		Color color = get_color("font_color", "Tree");
-		draw_string(font, Point2(hs, font->get_ascent() + (h - font->get_height()) / 2).floor(), label, color, get_size().width);
+		draw_string(font, Point2(Math::round((16 + arrow_margin) * EDSCALE), font->get_ascent() + (h - font->get_height()) / 2).floor(), label, color, get_size().width);
 
 		if (arrow.is_valid()) {
-			draw_texture(arrow, Point2(get_size().width - arrow->get_width(), (h - arrow->get_height()) / 2).floor());
+			draw_texture(arrow, Point2(Math::round(arrow_margin * EDSCALE), (h - arrow->get_height()) / 2).floor());
 		}
 	}
 }

editor/editor_themes.cpp

@@ -685,7 +685,6 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 	// Tree
 	theme->set_icon("checked", "Tree", theme->get_icon("GuiChecked", "EditorIcons"));
 	theme->set_icon("unchecked", "Tree", theme->get_icon("GuiUnchecked", "EditorIcons"));
-	theme->set_icon("arrow_up", "Tree", theme->get_icon("GuiTreeArrowUp", "EditorIcons"));
 	theme->set_icon("arrow", "Tree", theme->get_icon("GuiTreeArrowDown", "EditorIcons"));
 	theme->set_icon("arrow_collapsed", "Tree", theme->get_icon("GuiTreeArrowRight", "EditorIcons"));
 	theme->set_icon("updown", "Tree", theme->get_icon("GuiTreeUpdown", "EditorIcons"));

editor/icons/icon_arrow_up.svg

@@ -1,5 +0,0 @@
-<svg width="16" height="16" version="1.1" viewBox="0 0 16 16" xmlns="http://www.w3.org/2000/svg">
-<g transform="translate(0 -1036.4)">
-<path d="m2.9875 1044.4a1.0001 1.0001 0 0 0 1.7168 0.6972l2.293-2.2929v4.5859a1.0001 1.0001 0 1 0 2 0v-4.5859l2.293 2.2929a1.0001 1.0001 0 1 0 1.4141 -1.414l-3.9141-3.9141a1.0001 1.0001 0 0 0 -1.5859 0 1.0001 1.0001 0 0 0 -0.00391 0.01l-3.9102 3.9102a1.0001 1.0001 0 0 0 -0.30273 0.7168z" color="#000000" color-rendering="auto" dominant-baseline="auto" fill="#e0e0e0" fill-opacity=".99608" image-rendering="auto" shape-rendering="auto" solid-color="#000000" style="font-feature-settings:normal;font-variant-alternates:normal;font-variant-caps:normal;font-variant-ligatures:normal;font-variant-numeric:normal;font-variant-position:normal;isolation:auto;mix-blend-mode:normal;shape-padding:0;text-decoration-color:#000000;text-decoration-line:none;text-decoration-style:solid;text-indent:0;text-orientation:mixed;text-transform:none;white-space:normal"/>
-</g>
-</svg>