Improved strategy for reset to bootloader, fixing nodemcu reset issue

[abhra0897]

Improved strategy for resetting to the bootloader. Without this, the boot button of NodeMCU-ESP32 DevKITV1 has to be pressed manually in order to enter the bootloader. But with this fix, it automatically enters the bootloader.

The reset strategy and sequence have been taken from the official esptool code.

Also added hard_reset() calls at the end of the read and write functions.