debug: coredump: add xtensa coredump

Adds Xtensa as supported architecture for coredump. Fixes
a few typos in documentation, Kconfig and a C file. Dumps
minimal set of registers shown by 'info registers' in GDB
for the sample_controller and ESP32 SOCs. Updates tests.

Signed-off-by: Lauren Murphy <lauren.murphy@intel.com>
9 files changed