runner/runner_tests: add a test to check case-insensitive match

As regular expressions are now case-insensitive, add ab
unit test to verify that case-insensitive logic is working
as expected.

CC: Petri Latvala <adrinael@adrinael.net>
Reviewed-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>