Fix code folding icon color not matching defined color

Cherrypick of #58457 in master

Caused by reusing icons from the main editor in the code editor. These
icons were converted based on the main editor theme and not the code
editor theme.

    - Create new icons for use specifically in the code editor
    - Add these icons to the exceptions when converting dark theme icons
    to light theme automatically
    - Change the default value of the code folding color to match previous
    color
    - Code folding icon is now pure white by default to correctly match
    the color defined in settings

editor/editor_themes.cpp

@@ -233,6 +233,14 @@ void editor_register_and_generate_icons(Ref<Theme> p_theme, bool p_dark_theme =
 		exceptions.insert("StatusSuccess");
 		exceptions.insert("StatusWarning");
 		exceptions.insert("OverbrightIndicator");
+
+		// Prevents Code Editor icons from changing
+		exceptions.insert("GuiTab");
+		exceptions.insert("GuiSpace");
+		exceptions.insert("GuiEllipsis");
+		exceptions.insert("TextEditFold");
+		exceptions.insert("TextEditFolded");
+		exceptions.insert("TextEditorPlay");
 	}
 
 	// These ones should be converted even if we are using a dark theme.
@@ -986,8 +994,8 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 	theme->set_constant("side_margin", "TabContainer", 0);
 	theme->set_icon("tab", "TextEdit", theme->get_icon("GuiTab", "EditorIcons"));
 	theme->set_icon("space", "TextEdit", theme->get_icon("GuiSpace", "EditorIcons"));
-	theme->set_icon("folded", "TextEdit", theme->get_icon("GuiTreeArrowRight", "EditorIcons"));
-	theme->set_icon("fold", "TextEdit", theme->get_icon("GuiTreeArrowDown", "EditorIcons"));
+	theme->set_icon("folded", "TextEdit", theme->get_icon("TextEditFolded", "EditorIcons"));
+	theme->set_icon("fold", "TextEdit", theme->get_icon("TextEditFold", "EditorIcons"));
 	theme->set_color("font_color", "TextEdit", font_color);
 	theme->set_color("font_color_readonly", "TextEdit", font_color_readonly);
 	theme->set_color("caret_color", "TextEdit", font_color);
@@ -1322,7 +1330,7 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 	const float mono_value = mono_color.r;
 	const Color alpha1 = Color(mono_value, mono_value, mono_value, 0.07);
 	const Color alpha2 = Color(mono_value, mono_value, mono_value, 0.14);
-	const Color alpha3 = Color(mono_value, mono_value, mono_value, 0.7);
+	const Color alpha3 = Color(mono_value, mono_value, mono_value, 0.27);
 
 	// editor main color
 	const Color main_color = dark_theme ? Color(0.34, 0.7, 1.0) : Color(0.02, 0.5, 1.0);

editor/icons/icon_text_edit_fold.svg

@@ -0,0 +1 @@
+<svg clip-rule="evenodd" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round" viewBox="0 0 12 12" xmlns="http://www.w3.org/2000/svg"><path d="m3 5 3 3 3-3" fill="none" stroke="#fff" stroke-width="2"/></svg>

editor/icons/icon_text_edit_folded.svg

@@ -0,0 +1 @@
+<svg clip-rule="evenodd" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round" viewBox="0 0 12 12" xmlns="http://www.w3.org/2000/svg"><path d="m4 9 3-3-3-3" fill="none" stroke="#fff" stroke-width="2"/></svg>

editor/icons/icon_text_editor_play.svg

@@ -0,0 +1 @@
+<svg height="16" viewBox="0 0 16 16" width="16" xmlns="http://www.w3.org/2000/svg"><path d="m4 1048.4v-8l7 4z" fill="#e0e0e0" fill-rule="evenodd" stroke="#e0e0e0" stroke-linejoin="round" stroke-width="2" transform="translate(0 -1036.4)"/></svg>

scene/gui/text_edit.cpp

@@ -5444,7 +5444,7 @@ void TextEdit::_update_caches() {
 	cache.folded_icon = get_icon("folded");
 	cache.can_fold_icon = get_icon("fold");
 	cache.folded_eol_icon = get_icon("GuiEllipsis", "EditorIcons");
-	cache.executing_icon = get_icon("MainPlay", "EditorIcons");
+	cache.executing_icon = get_icon("TextEditorPlay", "EditorIcons");
 	text.set_font(cache.font);
 
 	if (syntax_highlighter) {