ReflectionProperty::__toString() renders const-expression defaults as source instead of the evaluated value

[lisachenko]

Pre-existing parity gap documented during the #223 investigation (see PR #228, "Deliberately not fixed" notes; kept out of that PR's scope).

For a property default that is a constant expression, e.g.:

class Migration {
    public const PREFIX = 'migration_';
    public string $table = self::PREFIX . 'books';
}

Go\ParserReflection\ReflectionProperty::__toString() renders the default as the source expression (self::PREFIX . 'books'), while native reflection renders the evaluated value ('migration_books'). getDefaultValue() already evaluates correctly via NodeExpressionResolver — only the string rendering diverges.

Expected: __toString() prints the evaluated default like native reflection.

[lisachenko]

Not a first priority, this tricky to achieve and constantly breaks