jni: Switch to @FastNative for all JNI functions. Deprecate !bang JNI.

Switches all (248) methods that previously used !bang JNI in art/libcore
to all use @FastNative.

Also deprecate !bang JNI since nothing in Android seems to (or should
be) using it anymore.

This measures to be a 3% startup time improvement in system_server.

Test: make test-art-host
Bug: 34955272
Change-Id: I0881f401c7660c79f275235362777bfa58241deb
diff --git a/runtime/native/java_lang_reflect_Proxy.cc b/runtime/native/java_lang_reflect_Proxy.cc
index 70cd6aa..0279b5f 100644
--- a/runtime/native/java_lang_reflect_Proxy.cc
+++ b/runtime/native/java_lang_reflect_Proxy.cc
@@ -35,7 +35,7 @@
 }
 
 static JNINativeMethod gMethods[] = {
-  NATIVE_METHOD(Proxy, generateProxy, "!(Ljava/lang/String;[Ljava/lang/Class;Ljava/lang/ClassLoader;[Ljava/lang/reflect/Method;[[Ljava/lang/Class;)Ljava/lang/Class;"),
+  FAST_NATIVE_METHOD(Proxy, generateProxy, "(Ljava/lang/String;[Ljava/lang/Class;Ljava/lang/ClassLoader;[Ljava/lang/reflect/Method;[[Ljava/lang/Class;)Ljava/lang/Class;"),
 };
 
 void register_java_lang_reflect_Proxy(JNIEnv* env) {