Allow context definition annotations to specify constraints

Problem/Motivation

In Layout Builder we have

*   context_definitions = {
 *     "entity" = @ContextDefinition("entity"),
 *     "view_mode" = @ContextDefinition("string", required = FALSE),
 *   }

with an accompanying plugin alter hook that does

  $definitions['overrides']->getContextDefinition('entity')
    ->addConstraint('EntityHasField', OverridesSectionStorage::FIELD_NAME);

Ideally we would be able to do something like

*   context_definitions = {
 *     "entity" = @ContextDefinition("entity")->addConstraint('EntityHasField', OverridesSectionStorage::FIELD_NAME),
 *     "view_mode" = @ContextDefinition("string", required = FALSE),
 *   }

or even

*   context_definitions = {
 *     "entity" = @ContextDefinition("entity", ['EntityHasField' => OverridesSectionStorage::FIELD_NAME]),
 *     "view_mode" = @ContextDefinition("string", required = FALSE),
 *   }

Proposed resolution

Add handling for constraints to \Drupal\Core\Annotation\ContextDefinition allowing annotations like this:

 *   context_definitions = {
 *     "entity" = @ContextDefinition("entity", constraints = {
 *       "EntityHasField" = \Drupal\layout_builder\Plugin\SectionStorage\OverridesSectionStorage::FIELD_NAME,
 *     }),
 *     "view_mode" = @ContextDefinition("string", required = FALSE),
 *   }

Remaining tasks

Write tests

User interface changes

N/A

API changes

N/A

Data model changes

N/A

Release notes snippet