Add force_suspend function

This CL implements a simple force_suspend().  This function takes a
timeoutMs argument that is currently ignored.  It also uses a two-stage
init process that spawns the suspend_thread when autosuspend is in use.

Follow-up CLs will:
- Implement file locking to prevent multiple libsuspend instances from
starting multiple suspend threads in the system.
- Fully implement timout for force_suspend.
- Integrate force_suspend with suspend_thred.

Bug: 70669809
Test:  autosuspend still works
Change-Id: I6b2c72d0c61d1bec6db0f0b28481ffe0e20ec615