Add a flag that makes dumpstate wait for options

There are 2 ways of running bugreports. Running dumpstate binary
directly with command line options (existing flow), or running the
binary to start the binder service, which waits for a caller to supply
arguments like file descriptors to write output to (new flow to support
the bugreport triggering API).

Support the second flow with a new commandline flag.

Also add a new service that uses the flag, to be used in the API.

BUG:111441001
Test: adb shell setprop "ctl.start" "bugreportd" -> starts service &
waits.
Test: interactive bugreport still works
Change-Id: I64cd03d15f45a896692d7462998d4faa6e413ef1