3.0: [UX] contextual only fields

## The problem to solve

In some cases (maybe a lot of cases in fact) `area` field type is not meant to be edited in admin modal mode but directly on the page - this is the majority of the cases in my current project and I'm not aware of any 'official' way of doing that via field options. The reasons for that need vary based on the context, but the outcome is the same. It may be an accessibility issue (not enough space for the produced widget output), missing style as it's `sandboxed` to the main content to no interfere with apos administration styles, combination of both and many more (actually real life cases now).

There are also cases when one wants a contextual only widget (as it was done in apos v2 as far as I know) but I consider this as a very minor UX issue.

## Proposed solution
Introduce an `area` specific field type option to skip rendering the are in modal edit mode. A simple rule would be skipped fields don't have validation (this can not be set as `required`).

The issue names no files or tests. Start by tracing how area fields render in admin modal mode versus directly on the page, then determine where a contextual-only option belongs. Done means the option skips modal rendering and skipped fields cannot be required or validated there.

Written by the indexing model from the issue text.