Change CountryConstraint plugin ID to avoid collision with Address contrib module.

src/Plugin/FieldValidationRule/CountryConstraintFieldValidationRule.php

@@ -21,7 +21,7 @@ class CountryConstraintFieldValidationRule extends ConstraintFieldValidationRule
    * {@inheritdoc}
    */
   public function getConstraintName(): string{
-    return "Country";
+    return "SymfonyCountry";
   }
 
   /**

src/Plugin/Validation/Constraint/CountryConstraint.php

@@ -9,7 +9,7 @@ use Symfony\Component\Validator\Constraints\CountryValidator;
  * Country constraint.
  *
  * @Constraint(
- *   id = "Country",
+ *   id = "SymfonyCountry",
  *   label = @Translation("Country", context = "Validation"),
  * )
  */