Subscribe fields with interest groups

The MailChimp subscribe experience when a list has interest groups enabled is pretty bad. The current behavior exposes both the subscribe for the list itself and the interests as well, but there isn't any logic to subscribe a user to the list if they only check an interest group for instance. Here is a proposed change for subscribe fields with interest groups:

MailChimp field on /user/register form
This would display only the interest groups if they exist and the user would be automatically "Subscribed" to the list if any interest group is checked.

[Newsletter Subscription Label]
Interest Group
Interest Group

MailChimp field on user form
This would be similar to the account creation form, but would also include an "Unsubscribe" checkbox to unsubscribe the user. If this option was checked by the user, all interest groups would be unchecked and the user would be unsubscribed.

[Newsletter Subscription Label]
Interest Group
Interest Group
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Unsubscribe from all