kunit: tool: add support for filtering suites by glob

This allows running different subsets of tests, e.g.

$ ./tools/testing/kunit/kunit.py build
$ ./tools/testing/kunit/kunit.py exec 'list*'
$ ./tools/testing/kunit/kunit.py exec 'kunit*'

This passes the "kunit_filter.glob" commandline option to the UML
kernel, which currently only supports filtering by suite name.

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>