Add "states" to terms list table (for WP_Taxonomy::$default_term)

[johnjamesjacoby]

The Terms list table (WP_Terms_List_Table) should include support for the "states" concept that currently also exists for Posts, Media, and Sites.

Specifically, I'd like to see "– Default" added to the default term.

I want this because WordPress Admin does not offer any explanation why the "Uncategorized" Category has no "Delete" link in the list-table UI and also has no checkbox for bulk-actions.

See: _post_states(), _media_states(), and WP_MS_Sites_List_Table::site_states()

Mock-up screenshot imminent.

[johnjamesjacoby]

Mocked up "– Default" term state