uart: esp32: move hal instance to data level
uart: esp32: move hal instance to data level

After #41918, DEV_CFG removal triggered discard qualifer warning
during build. As uart_hal functions don't required const qualifier
and uart_context_hal_t has modified data, this PR moves hal instace
to data struct instead of config struct.

Signed-off-by: Sylvio Alves <bd63183a3ab542e2b25ff1e90971d4881e1bdbe5@espressif.com>

galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr