Use common prefix for MicrodroidBenchmarks metrics

Data collection backend requires a filter for metrics to be collected.
To this end, establish a naming scheme. All AVF benchmarks to start with
'avf_perf/', all Microdroid benchmarks with 'avf_perf/microdroid/'.

Test: atest MicrodroidBenchmarks
Change-Id: I4794b118915f9d99acd23e1a85e9d24070b42dc6
diff --git a/tests/benchmark/src/java/com/android/microdroid/benchmark/MicrodroidBenchmarks.java b/tests/benchmark/src/java/com/android/microdroid/benchmark/MicrodroidBenchmarks.java
index 8adc8d7..5999af7 100644
--- a/tests/benchmark/src/java/com/android/microdroid/benchmark/MicrodroidBenchmarks.java
+++ b/tests/benchmark/src/java/com/android/microdroid/benchmark/MicrodroidBenchmarks.java
@@ -282,7 +282,7 @@
         assertThat(found).isTrue();
 
         Bundle bundle = new Bundle();
-        bundle.putInt("microdroid_minimum_required_memory", minimum);
+        bundle.putInt("avf_perf/microdroid/minimum_required_memory", minimum);
         mInstrumentation.sendStatus(0, bundle);
     }
 }