Regression: category selector missing on site wide contact form

The ability to select a contact category form is missing from the site wide contact form.

To reproduce:

1. Install standard profile
2. Add an additional contact category
3. View /contact

What the will look like

What's missing

Depends on the issue

#1477802: Shorter description for contact category weight
#599770: Clean up the contact category listing UI: Allow to set the default category and weights on the listing page

current approach

Introduce a block with a list of contact forms
Rename contact entity #2285083: Rename contact category to contact form

Originally was:
Suggests to use tabs #1849158: Expose contact category-specific forms and/or their URLs somewhere

Related #1866998: Introduce tab expansion facility for local tasks that are based on configuration