bootstat: Add some reserved sys.boot.reason values to enumeration

Add cold,powerkey, warm,s3_wakeup and hard,hw_reset so that
sys.boot.reason values can also be enumerated.  Also add
some reserved speculative entries associated with forced
suspend to RAM and DISK; shutdown,suspend and shutdown,hibernate
respectively.

Test: system/core/bootstat/boot_reason_test.sh
Bug: 67636061
Change-Id: Ic43523748e6006aaca882f8eec7c1f0c08431bd8