Defer requiring Rake until it's needed.

Eagerly requiring Rake could put 100ms on to the Rails boot time. Shimmy that
down to 0 by requiring Rake when no native Rails command exists and we try to
run a Rake task. Or when printing all the Rake commands through `rails help`.

Fixes rails#25029

Author: kaspth

railties/lib/rails/commands/rake_proxy.rb

@@ -1,10 +1,11 @@
-require "rake"
 require "active_support"
 
 module Rails
   module RakeProxy #:nodoc:
     private
       def run_rake_task(command)
+        require_rake
+
         ARGV.unshift(command) # Prepend the command, so Rake knows how to run it.
 
         Rake.application.standard_exception_handling do
@@ -15,6 +16,8 @@ def run_rake_task(command)
       end
 
       def rake_tasks
+        require_rake
+
         return @rake_tasks if defined?(@rake_tasks)
 
         ActiveSupport::Deprecation.silence do
@@ -30,5 +33,9 @@ def rake_tasks
       def formatted_rake_tasks
         rake_tasks.map { |t| [ t.name_with_args, t.comment ] }
       end
+
+      def require_rake
+        require "rake" # Defer booting Rake until we know it's needed.
+      end
   end
 end