Issue #3196822: Menu link attributes seems to break menu item translation

When a menu link entity was built on form submission, the attributes were not set on it and were saved later in the own form submit callback. This mismatch with the original entity caused the validation error. Using entity builder to set the attributes values fixes the issue.

Other than that translation settings are made to be respected: the attributes values are shared among all translations, and the attributes field set is hidden on translated menu item form when it's set to hide untranslatable fields.