-Cleaned up find/replace bar for replace (made selection only default if selection exists), also made buttons look like buttons

-Fixed a bug related to theme propagation, may be able to solve #6443, #6302 and others. Please test.

tools/editor/plugins/script_editor_plugin.cpp

@@ -1513,6 +1513,7 @@ void ScriptEditor::edit(const Ref<Script>& p_script, bool p_grab_focus) {
 	}
 	ERR_FAIL_COND(!se);
 	tab_container->add_child(se);
+
 	se->set_edited_script(p_script);
 	se->set_tooltip_request_func("_get_debug_tooltip",this);
 	if (se->get_edit_menu()) {