Add getOperatorTokens() to ExpressionParserInterface to separate operator token registration from parser identity

src/ExpressionParser/AbstractExpressionParser.php

@@ -27,4 +27,9 @@ abstract class AbstractExpressionParser implements ExpressionParserInterface
     {
         return [];
     }
+
+    public function getOperatorTokens(): array
+    {
+        return [$this->getName(), ...$this->getAliases()];
+    }
 }