Fix regression in API controllers with view_cache_dependencies helper

[excid3]

Rails 8's API controllers now includes the Caching module by default (to support rate_limit in API controllers), but does not include the Helpers module.

This causes the jbuilder cache method to raise an exception because the Rails caching module does not add the helper_method :view_cache_dependencies since that's only added if helper_method exists.

helper_method :view_cache_dependencies if respond_to?(:helper_method)

Example error:

ActionView::Template::Error: undefined local variable or method `view_cache_dependencies' for an instance of #<Class:0x000000012a6da468>
    /Users/chris/.local/share/mise/installs/ruby/3.3.5/lib/ruby/gems/3.3.0/bundler/gems/rails-a5d1e10449c6/actionview/lib/action_view/helpers/cache_helper.rb:257:in `digest_path_from_template'
    /Users/chris/.local/share/mise/installs/ruby/3.3.5/lib/ruby/gems/3.3.0/bundler/gems/rails-a5d1e10449c6/actionview/lib/action_view/helpers/cache_helper.rb:271:in `fragment_name_with_digest'
    /Users/chris/.local/share/mise/installs/ruby/3.3.5/lib/ruby/gems/3.3.0/bundler/gems/rails-a5d1e10449c6/actionview/lib/action_view/helpers/cache_helper.rb:252:in `cache_fragment_name'
    /Users/chris/.local/share/mise/installs/ruby/3.3.5/lib/ruby/gems/3.3.0/gems/jbuilder-2.13.0/lib/jbuilder/jbuilder_template.rb:227:in `_fragment_name_with_digest'
    /Users/chris/.local/share/mise/installs/ruby/3.3.5/lib/ruby/gems/3.3.0/gems/jbuilder-2.13.0/lib/jbuilder/jbuilder_template.rb:214:in `_cache_key'
    /Users/chris/.local/share/mise/installs/ruby/3.3.5/lib/ruby/gems/3.3.0/gems/jbuilder-2.13.0/lib/jbuilder/jbuilder_template.rb:194:in `_cache_fragment_for'
    /Users/chris/.local/share/mise/installs/ruby/3.3.5/lib/ruby/gems/3.3.0/gems/jbuilder-2.13.0/lib/jbuilder/jbuilder_template.rb:69:in `cache!'
    app/views/users/_user.json.jbuilder:1:in `_app_views_users__user_json_jbuilder___1927266165303472685_95340'

This adds the helper method to jbuilder to ensure that caching still works without having to include Helpers in API controllers.

Previously, this worked because you could include both the Helpers and Caching modules in API controllers in the correct order.

jbuilder doesn't have a test/dummy app to write tests for this.