Fix broken references to classic mode guide where possible and use new guide...

Fix broken references to classic mode guide where possible and use new guide where appropriate (#39603) [ci skip]

guides/source/configuring.md

@@ -62,7 +62,7 @@ These configuration methods are to be called on a `Rails::Railtie` object, such
 
 * `config.autoload_once_paths` accepts an array of paths from which Rails will autoload constants that won't be wiped per request. Relevant if `config.cache_classes` is `false`, which is the case in development mode by default. Otherwise, all autoloading happens only once. All elements of this array must also be in `autoload_paths`. Default is an empty array.
 
-* `config.autoload_paths` accepts an array of paths from which Rails will autoload constants. Default is all directories under `app`. It is no longer recommended to adjust this. See [Autoloading and Reloading Constants](autoloading_and_reloading_constants.html#autoload-paths-and-eager-load-paths)
+* `config.autoload_paths` accepts an array of paths from which Rails will autoload constants. Default is all directories under `app`. It is no longer recommended to adjust this. See [Autoloading and Reloading Constants](autoloading_and_reloading_constants.html#autoload-paths)
 
 * `config.add_autoload_paths_to_load_path` says whether autoload paths have to be added to `$LOAD_PATH`. This flag is `true` by default, but it is recommended to be set to `false` in `:zeitwerk` mode early, in `config/application.rb`. Zeitwerk uses absolute paths internally, and applications running in `:zeitwerk` mode do not need `require_dependency`, so models, controllers, jobs, etc. do not need to be in `$LOAD_PATH`. Setting this to `false` saves Ruby from checking these directories when resolving `require` calls with relative paths, and saves Bootsnap work and RAM, since it does not need to build an index for them.
 

guides/source/engines.md

@@ -240,8 +240,8 @@ applications into engines.
 
 NOTE: Because of the way that Ruby does constant lookup you may run into a situation
 where your engine controller is inheriting from the main application controller and
-not your engine's application controller. Ruby is able to resolve the `ApplicationController` constant, and therefore the autoloading mechanism is not triggered. See the section [When Constants Aren't Missed](autoloading_and_reloading_constants.html#when-constants-aren-t-missed) of the [Autoloading and Reloading Constants](autoloading_and_reloading_constants.html) guide for further details. The best way to prevent this from
-happening is to use `require_dependency` to ensure that the engine's application
+not your engine's application controller. Ruby is able to resolve the `ApplicationController` constant, and therefore the autoloading mechanism is not triggered. See the section [When Constants Aren't Missed](autoloading_and_reloading_constants_classic_mode.html#when-constants-aren-t-missed). 
+The best way to prevent this from happening is to use `require_dependency` to ensure that the engine's application
 controller is loaded. For example:
 
 ``` ruby