PM: hibernate: add configurable delay for pm_test

Turn the default 5 second test delay for hibernation into a
configurable module parameter, so users can determine how
long to wait in this pseudo-hibernate state before resuming
the system.

The configurable delay parameter has been added for suspend, so
add an analogous one for hibernation.

Example (wait 30 seconds);

  # echo 30 > /sys/module/hibernate/parameters/pm_test_delay
  # echo core > /sys/power/pm_test

Signed-off-by: Zihuan Zhang <zhangzihuan@kylinos.cn>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20250507063520.419635-1-zhangzihuan@kylinos.cn


[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>