Override `respond_to_missing?` instead of `respond_to?` when possible

This was almost every case where we are overriding `respond_to?` in a
way that mirrors a parallel implementation of `method_missing`. There is
one remaining case in Active Model that should probably do the same
thing, but had a sufficiently strange implementation that I want to
investigate it separately.

Fixes #26333.

actionpack/lib/action_dispatch/routing/routes_proxy.rb

@@ -19,7 +19,7 @@ def url_options
         end
       end
 
-      def respond_to?(method, include_private = false)
+      def respond_to_missing?(method, include_private = false)
         super || @helpers.respond_to?(method)
       end
 

actionpack/lib/action_dispatch/testing/integration.rb

@@ -502,7 +502,7 @@ def default_url_options=(options)
         integration_session.default_url_options = options
       end
 
-      def respond_to?(method, include_private = false)
+      def respond_to_missing?(method, include_private = false)
         integration_session.respond_to?(method, include_private) || super
       end
 

activerecord/lib/active_record/dynamic_matchers.rb

@@ -2,7 +2,7 @@
 
 module ActiveRecord
   module DynamicMatchers #:nodoc:
-    def respond_to?(name, include_private = false)
+    def respond_to_missing?(name, include_private = false)
       if self == Base
         super
       else

activerecord/lib/active_record/migration/command_recorder.rb

@@ -92,7 +92,7 @@ def inverse_of(command, args, &block)
         send(method, args, &block)
       end
 
-      def respond_to?(*args) # :nodoc:
+      def respond_to_missing?(*args) # :nodoc:
         super || delegate.respond_to?(*args)
       end
 

activerecord/lib/active_record/relation/delegation.rb

@@ -108,7 +108,7 @@ def relation_class_for(klass)
         end
     end
 
-    def respond_to?(method, include_private = false)
+    def respond_to_missing?(method, include_private = false)
       super || @klass.respond_to?(method, include_private) ||
         arel.respond_to?(method, include_private)
     end