tests: framework: fix code coverage report on zephyr-sdk-0.15

The GCC/GCOV version over 12 has slight format change of the gcno
and gcda. Make some adaption in the gcov dump function to fix the
code coverage report.

Mainly two places change:
1. Added the checksum in the struct gcov_info. This fix the crash
in qemu_x86, and mps2_an385 when run with --coverage.

2. Adjust the GCOV_TAG_FUNCTION_LENGTH accroding to gcov-io.h. It's
length unit is caculated by bytes now.

Fixes #50255.
Fixes #50257.

Signed-off-by: Enjia Mai <enjia.mai@intel.com>