ART: Add GetPhase

Extend RuntimePhaseCallback. Add support for GetPhase.
Add tests.

Bug: 31455788
Test: m test-art-host-run-test-901-hello-ti-agent
Change-Id: I33b1934a0789bc713675f21c2c9f676c9d3a1ed1
diff --git a/test/901-hello-ti-agent/src/Main.java b/test/901-hello-ti-agent/src/Main.java
index 775e5c2..faf2dc2 100644
--- a/test/901-hello-ti-agent/src/Main.java
+++ b/test/901-hello-ti-agent/src/Main.java
@@ -20,6 +20,10 @@
 
     System.out.println("Hello, world!");
 
+    if (checkLivePhase()) {
+      System.out.println("Agent in live phase.");
+    }
+
     set(0);  // OTHER
     set(1);  // GC
     set(2);  // CLASS
@@ -37,5 +41,6 @@
     }
   }
 
+  private static native boolean checkLivePhase();
   private static native void setVerboseFlag(int flag, boolean value);
 }