Add suggestions for form actions container

Problem/Motivation

The form actions container only has the suggestion of container__[form-id]. It would be nice if formdazzle used a container__actions__[form-id] suggestion.

Proposed resolution

Looking through all the Drupal\Core\Render\Elements, these are all the core element types that need a generic theme suggestion: actions, more_link, password_confirm, and system_compact_link.

We will change all of those elements suggestions from [hook]__[form-id] to [hook]__[type]__[form-id].

API changes

The 8.x-1.0-rc1 and earlier suggestions for those element types (which look like [hook]__[form-id]) will break as they will be replaced with suggestions that look like [hook]__[type]__[form-id].