1. separate rom include files and linkscript to esp_rom
2. modefiy "include rom/xxx.h" to "include esp32/rom/xxx.h"
3. Forward compatible
4. update mqtt
In some cases, linker could choose to use ROM functions instead of the
ones defined in IDF.
For functions used in ROM stub table, this would lead to infinite
recursion when the corresponding function was called from ROM.
For crypto functions, some of these were modified in IDF, and
incompatible with ROM counterparts.