tests: lifo_usage: make it less susceptible to SMP races

On SMP, and especially using qemu on a busy system, it is possible for
a thread with a later timeout to get ahead of another one with an
earlier timeout. The tight timeout value difference (10ms) makes it
possible albeit difficult to reproduce. The result is something like:

|START - test_timeout_threads_pend_on_lifo
| thread (q order: 2, t/o: 0, lifo 0x4001d350)
|
|    Assertion failed at main.c:140:
|test_multiple_threads_pending: (data->timeout_order not equal to ii)
| *** thread 2 woke up, expected 1

Let's make timeout values 10 times larger to make this unlikely race
even less likely.

While at it... The timeout field in struct timeout_order_data is some ms
value and not a number of ticks, so change the type accordingly.
And leverage k_cyc_to_ms_floor32() to simplify computation in
is_timeout_in_range().

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>