Fix drupal 10 deprecations

Problem/Motivation

 ------ ----------------------------------------------------------------------- 
  Line   tests/src/Unit/Plugin/freelinking/NodeTitleFailoverTest.php            
 ------ -----------------------------------------------------------------------              
  79     Property                                                               
         Drupal\Tests\freelinking\Unit\Plugin\freelinking\NodeTitleFailoverTes  
         t::$container (Drupal\Core\DependencyInjection\Container) does not     
         accept Drupal\Core\DependencyInjection\ContainerBuilder.               
 ------ ----------------------------------------------------------------------- 

 ------ ----------------------------------------------------------------------- 
  Line   tests/src/Unit/Plugin/freelinking/UserTest.php                         
 ------ -----------------------------------------------------------------------                      
  66     Access to an undefined property                                        
         Drupal\Tests\freelinking\Unit\Plugin\freelinking\UserTest::$container  
         .                                                                      
  75     Property                                                               
         Drupal\Tests\freelinking\Unit\Plugin\freelinking\UserTest::$plugin     
         (Drupal\freelinking\Plugin\freelinking\Node) does not accept           
         Drupal\freelinking\Plugin\freelinking\User.                            
 ------ ----------------------------------------------------------------------- 

 ------ ----------------------------------------------------------------------- 
  Line   tests/src/Unit/Plugin/freelinking/UserUnauthorizedTest.php             
 ------ -----------------------------------------------------------------------                 
  54     Access to an undefined property                                        
         Drupal\Tests\freelinking\Unit\Plugin\freelinking\UserUnauthorizedTest  
         ::$container.                                                          
  63     Property                                                               
         Drupal\Tests\freelinking\Unit\Plugin\freelinking\UserUnauthorizedTest  
         ::$plugin (Drupal\freelinking\Plugin\freelinking\Node) does not        
         accept Drupal\freelinking\Plugin\freelinking\User.                     
 ------ ----------------------------------------------------------------------- 

Proposed resolution

Use new things deprecated from 9.1.0 or greater.
Fixes prophecy usage.
Fixes tags.

Fix in 4.0.x branch. Can use merge request.

API changes

Removes deprecations in 9.1.0 or greater.