Add debug dumping to safepower_agent.

This change introduces methods to dump the state of running actions and system states. A SIGUSR1 signal handler is added to gpowerd to trigger a debug dump to `/tmp/gpowerd_dbg`, including details from ActionContextManager and the system state updaters.

example usage:
kill -10 $(pidof gpowerd)
https://paste.googleplex.com/5914979863756800?raw

PiperOrigin-RevId: 856718698
Change-Id: I9f8b70fac45a4160b8404f951ff7ff0536541b9f