Change automatic body field creation to use formatted text field instead of text_with_summary

Problem/Motivation

#3447617: Stop automatic storage creation of body field will not make it in by the Starshot release, so we need to consider what is the least disruptive in the meantime.

Proposed resolution

The data model will use the regular formatted text field instead of text_with_summary, so we discussed at DrupalCon Barcelona that that the best strategy is to change the automatic field to be a regular formatted text field instead of using text_with_summary.

Remaining tasks

1. Agree on the name for the field (body vs. something else)
2. Make the change (and update tests if needed?)
3. Review
4. Commit and flourish

User interface changes

N/A

Introduced terminology

N/A

API changes

N/A

Data model changes

N/A

Release notes snippet

N/A