Schema: Improving Delete and Duplicate Model Experience + Minor UX Enhancements

[zcolah]

Very Important (Users have requested):

1. Schema: Add Delete Model and Duplicate Model Buttons  (Ben, Dan)
2. Schema: Edit Model Screen - Update Chevron in top bar to More Button Icon (Ben, Dan)
3. Schema: Add option to sort models by Last Modified (JJ)

Minor UX Enhancements

1. Schema: Edit Model Info Tab - Add placeholder/empty state value for description and parent model
2. Schema: Add 32 px margin below the "Add Another Field to " button

[zcolah]

@theofficialnar please add the following minor change request from a customer to this issue if possible:

Rename Label to Display Label (see screenshot). This should be done for all create field and edit field modals.