Make deprecate work for non-exists methods

Before #33325, `deprecate` works for non-exist methods.
This is necessary, for example, if want to deprecate dynamically defined
methods like attributes methods.

Fixes #34646

activesupport/lib/active_support/deprecation/method_wrappers.rb

@@ -52,8 +52,10 @@ def deprecate_methods(target_module, *method_names)
         options = method_names.extract_options!
         deprecator = options.delete(:deprecator) || self
         method_names += options.keys
+        mod = Module.new
 
         method_names.each do |method_name|
+          if target_module.method_defined?(method_name) || target_module.private_method_defined?(method_name)
             aliased_method, punctuation = method_name.to_s.sub(/([?!=])$/, ""), $1
             with_method = "#{aliased_method}_with_deprecation#{punctuation}"
             without_method = "#{aliased_method}_without_deprecation#{punctuation}"
@@ -72,7 +74,15 @@ def deprecate_methods(target_module, *method_names)
             when target_module.private_method_defined?(without_method)
               target_module.send(:private, method_name)
             end
-        end
+          else
+            mod.send(:define_method, method_name) do |*args, &block|
+              deprecator.deprecation_warning(method_name, options[method_name])
+              super(*args, &block)
+            end
+          end
+        end
+
+        target_module.prepend(mod) unless mod.instance_methods(false).empty?
       end
     end
   end

activesupport/test/deprecation_test.rb

@@ -31,6 +31,9 @@ def e; end
   def f=(v); end
   deprecate :f=
 
+  deprecate :g
+  def g ;end
+
   module B
     C = 1
   end
@@ -425,6 +428,10 @@ def test_custom_gem_name
     end
   end
 
+  def test_deprecate_work_before_define_method
+    assert_deprecated { @dtc.g }
+  end
+
   private
     def deprecator_with_messages
       klass = Class.new(ActiveSupport::Deprecation)