Jvm thread (#28)

* ADD: Add Thread

* MOD: modify type

language-agent/JVMMetric.proto

@@ -42,6 +42,7 @@ message JVMMetric {
     repeated Memory memory = 3;
     repeated MemoryPool memoryPool = 4;
     repeated GC gc = 5;
+    Thread thread = 6;
 }
 
 message Memory {
@@ -80,3 +81,9 @@ enum GCPhrase {
     OLD = 1;
 }
 
+message Thread {
+  int64 liveCount = 1;
+  int64 daemonCount = 2;
+  int64 peakCount = 3;
+}
+