Move some Unsafe.* methods to core platform API

These are used by the framework's protobuf implementation.

Test: compiles
Change-Id: I8a8aebbdd94c0012768b7a16732e708ee35714e6
diff --git a/openjdk_java_files.bp b/openjdk_java_files.bp
index 5c27228..c1f29ea 100644
--- a/openjdk_java_files.bp
+++ b/openjdk_java_files.bp
@@ -1387,6 +1387,7 @@
     srcs: [
         "ojluni/src/main/java/java/nio/DirectByteBuffer.java",
         "ojluni/src/main/java/sun/misc/Cleaner.java",
+        "ojluni/src/main/java/sun/misc/Unsafe.java",
         "ojluni/src/main/java/sun/nio/ch/DirectBuffer.java",
         "ojluni/src/main/java/sun/security/jca/Providers.java",
         "ojluni/src/main/java/sun/security/pkcs/ContentInfo.java",
@@ -1451,7 +1452,6 @@
         "ojluni/src/main/java/sun/misc/Resource.java",
         "ojluni/src/main/java/sun/misc/SharedSecrets.java",
         "ojluni/src/main/java/sun/misc/URLClassPath.java",
-        "ojluni/src/main/java/sun/misc/Unsafe.java",
         "ojluni/src/main/java/sun/misc/Version.java",
         "ojluni/src/main/java/sun/misc/VM.java",
         "ojluni/src/main/java/sun/net/ApplicationProxy.java",