This PR:
- fixes a broken pipe like in JeffLIrion#351, but from `grep -q` instead of `grep -m 1`
- uses a much more efficient call to get screen state

On Android 14, both `dumpsys power` greps no longer match. It prints
`Display Power: com.android.server.power.PowerManagerService$1@a8a75e6` with
no `state=` field, and `mScreenOn=true` is gone. So each poll, every 10
seconds, falls back to `dumpsys display`, a much more expensive call.

Because `grep -q` terminates on first match, the pipe is broken, resulting in
a stack trace every 10 seconds that looks like:

```
W FastPrintWriter: Write failure
W FastPrintWriter: java.io.IOException: write failed: EPIPE (Broken pipe)
W FastPrintWriter: 	at libcore.io.IoBridge.write(IoBridge.java:651)
W FastPrintWriter: 	at java.io.FileOutputStream.write(FileOutputStream.java:432)
W FastPrintWriter: 	at com.android.internal.util.FastPrintWriter.flushBytesLocked(FastPrintWriter.java:355)
W FastPrintWriter: 	at com.android.internal.util.FastPrintWriter.flushLocked(FastPrintWriter.java:378)
W FastPrintWriter: 	at com.android.internal.util.FastPrintWriter.flush(FastPrintWriter.java:413)
W FastPrintWriter: 	at android.os.Binder.dump(Binder.java:1158)
W FastPrintWriter: 	at android.os.Binder.onTransact(Binder.java:1022)
W FastPrintWriter: Caused by: android.system.ErrnoException: write failed: EPIPE (Broken pipe)
W FastPrintWriter: 	at libcore.io.IoBridge.write(IoBridge.java:646)
W FastPrintWriter: 	... 9 more
```

This PR fixes the issue:
- uses `dumpsys deviceidle get screen` to check screen state, which is cheap
  and has been available since Android 7
- removes `-q` so grep will not stop on first match and cause broken pipe