boards: esp32-based: update documentation

This PR updates all Espressif board names to meet its
original value. It also update reference links, re-organize
entries and removes unused content.

This also fixes bootloader information regarding a few boards.
IDF Bootloader was removed and these boards kept that info.
This updated it accordingly with the Simpleboot Bootloader.

Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>