scripts: tests: sanitycheck: Add testcases for TestCase class

test_testinstance.py: Add testcases to scan file and path for
sub testcases
test_data/testcases: Also added the ztest test files
test_testsuite_class.py: changed get_all_tests() to match
count of sub testcases in ztest files

Signed-off-by: Spoorthy Priya Yerabolu <spoorthy.priya.yerabolu@intel.com>
5 files changed