ftests/009: add cpu controller format (v2)

ftests/009: add cpu controller format (v2)

Starting Linux Kernel version 6.0, the cpu controller cpu.stat (v2)
additionally displays force_idle statistics. It was introduced by
upstream commit 1fcf54deb767 ("sched/core: add forced idle accounting
for cgroups"). Append a new expected output with the field
'core_sched.force_idle_usec' to cgroup v2 valid output.

-----------------------------------------------------------------
Test Results:
        Run Date:                          Apr 03 15:36:32
        Passed:                                  1 test(s)
        Skipped:                                 0 test(s)
        Failed:                                  0 test(s)
-----------------------------------------------------------------
Timing Results:
        Test                                    Time (sec)
        --------------------------------------------------
        setup                                         0.00
        009-cgget-g_flag_controller_only.py           0.10
        teardown                                      0.00
        --------------------------------------------------
        Total Run Time                                0.10

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>