Add CakePHP 6.0 rector rules for void return type changes

[dereuromark]

Summary

Add rector rules for upgrading to CakePHP 6.0, specifically handling methods that changed from returning bool to returning void.

New Rules:

1. RemoveAssignmentFromVoidMethodRector - Removes variable assignments from method calls that now return void:

   // Before
   $result = $this->request->allowMethod('post');
   
   // After
   $this->request->allowMethod('post');

2. Method Renames - Renames validChoice() to validateChoice() for console input classes

Affected Methods:

Class	Method	Change
ServerRequest	allowMethod()	Returns void
Configure	load()	Returns void
ResponseEmitter	emit()	Returns void
Session	close()	Returns void
Table	deleteOrFail()	Returns void
FixtureInterface	insert()	Returns void
FixtureInterface	truncate()	Returns void
ConsoleInputArgument	validChoice()	Renamed to validateChoice(), returns void
ConsoleInputOption	validChoice()	Renamed to validateChoice(), returns void

Related PRs:

• Change return type of methods which only return true to void. cakephp#19220
• Change return type of FixtureInterface::insert() and truncate() to void cakephp#19243