Update Method#duplicable? to be consistent with Ruby 3.4

Fix: https://github.com/rails/rails/issues/51075

`Method` and `UnboundMethod` used to raise on `#dup`, but not `#clone`,
this wasn't so much a feature, but a bug.

It was fixed in https://github.com/ruby/ruby/pull/9926.

activesupport/lib/active_support/core_ext/object/duplicable.rb

@@ -28,7 +28,15 @@ class Object
   end
 end
 
-class Method
+methods_are_duplicable = begin
+  Object.instance_method(:duplicable?).dup
+  true
+rescue TypeError
+  false
+end
+
+unless methods_are_duplicable
+  class Method
     # Methods are not duplicable:
     #
     #   method(:puts).duplicable? # => false
@@ -36,9 +44,9 @@ class Method
     def duplicable?
       false
     end
-end
+  end
 
-class UnboundMethod
+  class UnboundMethod
     # Unbound methods are not duplicable:
     #
     #   method(:puts).unbind.duplicable? # => false
@@ -46,6 +54,7 @@ class UnboundMethod
     def duplicable?
       false
     end
+  end
 end
 
 require "singleton"

activesupport/test/core_ext/object/duplicable_test.rb

@@ -6,18 +6,26 @@ require "active_support/core_ext/object/duplicable"
 require "active_support/core_ext/numeric/time"
 
 class DuplicableTest < ActiveSupport::TestCase
-  RAISE_DUP = [method(:puts), method(:puts).unbind, Class.new.include(Singleton).instance]
-  ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3, Complex(1), Rational(1)]
+  OBJECTS = [
+     method(:puts), method(:puts).unbind, Class.new.include(Singleton).instance,
+    "1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new,
+    Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3, Complex(1), Rational(1),
+  ]
 
-  def test_duplicable
-    RAISE_DUP.each do |v|
-      assert_not v.duplicable?, "#{ v.inspect } should not be duplicable"
-      assert_raises(TypeError, v.class.name) { v.dup }
+  OBJECTS.each do |v|
+    test "#{v.class}#duplicable? matches #{v.class}#dup behavior" do
+      duplicable = begin
+        v.dup
+        true
+      rescue TypeError
+        false
       end
 
-    ALLOW_DUP.each do |v|
-      assert_predicate v, :duplicable?, "#{ v.class } should be duplicable"
-      assert_nothing_raised { v.dup }
+      if duplicable
+        assert_predicate v, :duplicable?
+      else
+        assert_not_predicate v, :duplicable?
+      end
     end
   end
 end