Introduce suspend-to-hibernate (#8274)

Suspend to Hibernate is a new sleep method that invokes suspend
for a predefined period of time before automatically waking up
and hibernating the system.

It's similar to HybridSleep however there isn't a performance
impact on every suspend cycle.

It's intended to use with systems that may have a higher power
drain in their supported suspend states to prevent battery and
data loss over an extended suspend cycle.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>

src/basic/special.h

@@ -37,6 +37,7 @@
 #define SPECIAL_SUSPEND_TARGET "suspend.target"
 #define SPECIAL_HIBERNATE_TARGET "hibernate.target"
 #define SPECIAL_HYBRID_SLEEP_TARGET "hybrid-sleep.target"
+#define SPECIAL_SUSPEND_TO_HIBERNATE_TARGET "suspend-to-hibernate.target"
 
 /* Special boot targets */
 #define SPECIAL_RESCUE_TARGET "rescue.target"