Use method handles for binding ungenerated invokers

JRuby extensions can be bound using bytecode-generated invokers,
either pregenerated at build time or generated on the fly at
runtime. In the latter case, the overhead of failing to find a
pregenerated invoker, generating the new bytecode, and loading it
appears to be more expensive than using invokedynamic method
handles to do the binding. This PR enables using indy handles for
all non-generated method bindings at runtime.

core/src/main/java/org/jruby/util/cli/Options.java

@@ -83,7 +83,7 @@ public class Options {
     // ClassValue in OpenJDK appears to root data even after it goes away, so this is disabled again. See jruby/jruby#3228
     public static final Option<Boolean> INVOKEDYNAMIC_CLASS_VALUES = bool(INVOKEDYNAMIC, "invokedynamic.class.values", false, "Use ClassValue to store class-specific data.");
     public static final Option<Integer> INVOKEDYNAMIC_GLOBAL_MAXFAIL = integer(INVOKEDYNAMIC, "invokedynamic.global.maxfail", 100, "Maximum global cache failures after which to use slow path.");
-    public static final Option<Boolean> INVOKEDYNAMIC_HANDLES = bool(INVOKEDYNAMIC, "invokedynamic.handles", false, "Use MethodHandles rather than generated code to bind Ruby methods.");
+    public static final Option<Boolean> INVOKEDYNAMIC_HANDLES = bool(INVOKEDYNAMIC, "invokedynamic.handles", true, "Use MethodHandles rather than generated code to bind methods.");
     public static final Option<Boolean> INVOKEDYNAMIC_YIELD = bool(INVOKEDYNAMIC, "invokedynamic.yield", true, "Bind yields directly using invokedynamic.");
 
     // NOTE: -1 jit.threshold is way of having interpreter not promote full builds