ESP-IDF main Kconfig suggestion

[luca.gamma]

Here is just a suggestion to modify (for esthetical reason) the main Kconfig in ESP-IDF. In my opinion the main screen should include only menus while Optimization level is included as a choice. The generated sdkconfig file will then append the Optimization level option at the end of the Partition table options (or any other previous custom menu). Even for a single option could be advisable to have a menu to better distinguish the different sections in the sdkconfig file so I think it would be better to include Optimization level inside a menu for a better view.