nuplayer/2 emit state name, not number

augment both nuplayer and nuplayer2 so that the state information
they emit to media metrics for error exits is symbolic, not numeric.

Bug: 70525617
Test: manual
Change-Id: Ie43266cd75810ff4ea6e00f32a1666dc9a5a37dc
diff --git a/media/libmedia/nuplayer2/NuPlayer2Driver.h b/media/libmedia/nuplayer2/NuPlayer2Driver.h
index 051eba5..0028d05 100644
--- a/media/libmedia/nuplayer2/NuPlayer2Driver.h
+++ b/media/libmedia/nuplayer2/NuPlayer2Driver.h
@@ -115,6 +115,8 @@
         STATE_STOPPED_AND_PREPARED,     // equivalent to PAUSED, but seek complete
     };
 
+    std::string stateString(State state);
+
     enum {
         kWhatNotifyListener,
     };