Core dump can now be written in plain text if the partition itself is encrypted.
So it is important to modify the partition table if the user wants an encrypted
core dump partition as by default, it is not.
Added some functions in core_dump_port.c to abstract the checksum implementation
from core_dump_flash.c file.
Closes IDF-458
The coredump is now encrypted when saved on an encrypted flash.
The cache used for saving the file onto the flash is bigger,
making the proccess more efficient.
Relates to IDF-458
Closes https://github.com/espressif/esp-idf/issues/2932
Move existing core dump files into espcoredump component folder
Add KConfig, linker.lf, make and CMakeList.txt for new component
Existing functionality separated into core_dump_common, core_dump_flash, core_dump_uart
Update test_core_dump.c and make files to link it as unit test
Update according to review:
Move target and RTOS related functionality into separated file (core_dump_port.c).
