tests: kernel/common: incorrect use of k_poll in timeout order

In the timeout order test, the usage of k_poll() assumes that it
only returns after all events are ready. However, that is not
the case, as k_poll() returns when non-zero number of events are
ready. This means the check for all semaphore being ready after
k_poll() will not always pass. So instead of using k_poll(),
simply wait a bit for timers to fire, then check results.

Also add some bits to clean up at the end of test.

Fixes #34585

Signed-off-by: Daniel Leung <daniel.leung@intel.com>