Disable elements to disallow translators from making changes to the unit when they've chosen a non-default language. When they choose another language, we want them to focus on translating. This constraint also helps simplify our code.
Test
In the AT for a multi-lingual unit
authoring in default language works as before
when you switch to a non-default language,
you can translate text as before
you can't make changes to the unit in any other way, for example:
add/delete/move/copy steps/components
edit component content, like switching "Selection Type" or adding new choices in MC component
Changes
Test
In the AT for a multi-lingual unit