Allow template to return any kind of objects

Fix: https://github.com/rails/rails/issues/50930

While Action View is predominantly meant to render text,
in sime case it's used to render more complex object.

So we shouldn't assume `#_run` returns a buffer.

actionview/lib/action_view/template.rb

@@ -272,7 +272,8 @@ module ActionView
           view._run(method_name, self, locals, buffer, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)
           nil
         else
-          view._run(method_name, self, locals, OutputBuffer.new, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)&.to_s
+          result = view._run(method_name, self, locals, OutputBuffer.new, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)
+          result.is_a?(OutputBuffer) ? result.to_s : result
         end
       end
     rescue => e

actionview/test/template/template_test.rb

@@ -121,6 +121,14 @@ class TestERBTemplate < ActiveSupport::TestCase
     assert_equal "hellopartialhello", render
   end
 
+  def test_rendering_non_string
+    my_object = Object.new
+    eval_handler = ->(_template, source) { source }
+    @template = ActionView::Template.new("my_object", "__id__", eval_handler, virtual_path: "hello", locals: [:my_object])
+    result = render(my_object: my_object)
+    assert_same my_object, result
+  end
+
   def test_resulting_string_is_utf8
     @template = new_template
     assert_equal Encoding::UTF_8, render.encoding