Correcting HasEverPlayed metric entry (#3171)

Cobalt.Media.HasEverPlayed was correctly being logged as
base::UmaHistogramBoolean()
however, it was incorrectly using an enum for PipelineStatus.

This CL adds a new enum BooleanHasPlayed and sets
Cobalt.Media.HasEverPlayed to use it.
( I used a new enum rather than just the Boolean enum to follow
Chromium's example:

https://source.chromium.org/chromium/chromium/src/+/main:tools/metrics/histograms/metadata/media/histograms.xml;l=3891)

b/337308115

tools/metrics/histograms/metadata/cobalt/enums.xml

@@ -37,6 +37,11 @@ https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histogra
   <int value="1" label="True"/>
 </enum>
 
+<enum name="BooleanHasPlayed">
+  <int value="0" label="Never played"/>
+  <int value="1" label="Played"/>
+</enum>
+
 <enum name="PipelineStatus">
   <summary>
    Possible status values reported by the Media Pipeline

tools/metrics/histograms/metadata/cobalt/histograms.xml

@@ -119,15 +119,14 @@ Always run the pretty print utility on this file after editing:
   </summary>
 </histogram>
 
-<histogram name="Cobalt.Media.HasEverPlayed" enum="PipelineStatus"
+<histogram name="Cobalt.Media.HasEverPlayed" enum="BooleanHasPlayed"
     expires_after="never">
 <!-- expires-never: Needed for baseline Media pipeline health metric. -->
 
   <owner>[email protected]</owner>
   <owner>[email protected]</owner>
   <summary>
-    Status of the media pipeline at the end of its lifecycle for audio-video
-    streams with an unknown video codec.
+    Whether a given WebMediaPlayer instance, after preload, started playback;
   </summary>
 </histogram>