The former FLASH_MODE_{DOUT,DIO,QOUT,QIO} defines are replaced by the corresponding CONFIG_FLASHMODE_{DOUT,DIO,QOUT,QIO} and CONFIG_ESPTOOLPY_FLASHMODE_{DOUT,DIO,QOUT,QIO} as used by the ESP-IDF. This is also needed for the migration of defining flash mode in Kconfig.
Since a number of applications rely on the existence of the BTN0_PIN definition, the BUTTON0_PIN definition has been renamed to BTN0_PIN to make the ESP32 boards compatible with these applications. However, for compatibility with earlier versions, BUTTON0_PIN is still defined as an alias of BTN0_PIN.
SPI0_DEV and SPI1_DEV configuration parameters are renamed SPI0_CTRL and SPI1_CTRL to better describe what they define and to avoid confusion with SPI_DEV (0) and SPI_DEV (1).
Fixes the UART pin configuration for UART_DEV(0). Since this configuration is fixed and only defined for documentation purposes, the change has no impact on the code.
