Cleanup esp32 include directories

[balazsracz]

Certain critical include files are located in a different directory under esp-idf than under openmrn compilation.
On one hand, there are a bunch of internal includes in the toplevel of OpenMRNIDF. This is not nice.

This causes also unnecessary complexity in the includes (from #771 (comment) in Bootloader.hxx):

#ifdef ESP_PLATFORM
#include "bootloader_hal.h"
#else
#include "freertos/bootloader_hal.h"