preserve scripts panel visibility state between sessions in project metadata

hiding script's panel, helps some users to conserve more space for code text.
this fix remembers script's panel visibility state in project's metadata and restore it on editor start.
Thanks to this, users who never use it and are forced to close it each time editor starts, may close it just once and it will stay like this on next sessions until manually opened again.

editor/plugins/script_editor_plugin.cpp

@@ -992,6 +992,7 @@ Array ScriptEditor::_get_open_scripts() const {
 
 bool ScriptEditor::toggle_scripts_panel() {
 	list_split->set_visible(!list_split->is_visible());
+	EditorSettings::get_singleton()->set_project_metadata("scripts_panel", "show_scripts_panel", list_split->is_visible());
 	return list_split->is_visible();
 }
 
@@ -3223,6 +3224,7 @@ ScriptEditor::ScriptEditor(EditorNode *p_editor) {
 	overview_vbox->set_v_size_flags(SIZE_EXPAND_FILL);
 
 	list_split->add_child(overview_vbox);
+	list_split->set_visible(EditorSettings::get_singleton()->get_project_metadata("scripts_panel", "show_scripts_panel", true));
 	buttons_hbox = memnew(HBoxContainer);
 	overview_vbox->add_child(buttons_hbox);