Fix problem with accessing deprecated constant proxy's subclass

[sikachu]

This commit fixes #36313.

After #32065 moved SourceAnnotationExtractor into Rails module, it broke the ability to access SourceAnnotationExtractor::Annotate directly as user would get this error:

TypeError: Rails::SourceAnnotationExtractor is not a class/module

This commit fixes the issue by making DeprecatedConstantProxy to inherit from Module and then defines method_missing and const_missing to retain the previous functionality.

Thank you @matthewd for the idea of how to fix the issue!

[sikachu]

@matthewd I use @deprecator.warn just like in method_missing, and use const_get as your feedback. I also added another test just to make sure we get both NameError and deprecation message when someone tries to access a constant that isn't exist on the new constant.

Would you mind taking another look and merge it if you think it's good to go?

[sikachu]

I removed the new method. Ready for another look!

[sikachu]

@matthewd actually, removing that cause this test to fail (Waffles is set to false in this case):

rails/activesupport/test/deprecation/proxy_wrappers_test.rb

Lines 20 to 23 in a59b230

	def test_deprecated_constant_proxy_doesnt_wrap_falsy_objects
	proxy = ActiveSupport::Deprecation::DeprecatedConstantProxy.new(Waffles, NewWaffles)
	assert_not proxy
	end

So, I've brought back that self.new method to retain the functionality.

[matthewd]

I'll merge because this has been waiting on me for ages (🙈), but I think that's a bad test (this class expects to receive strings containing the old/new constant names, not actual constant references) and can be deleted.

[natevick]

🎉thanks to you all!