Update User Manual form to match Node form

Problem/Motivation

The User Manual entry form deviates from the standard form layout and labels that a node entry form has. Being consistent with Drupal core nodes would improve the authoring experience with this module.

Steps to reproduce

1. Add a new User Manual entry

Proposed resolution

1. Move the revision field to a sidebar field group
2. Move the URL alias to a sidebar field group labeled "URL alias"
3. Move the Authored by field to a sidebar field group labeled "Authoring information"
4. Rename the "Content" field to "Body"

See this mockup for guidance.

Remaining tasks

1. ❌ Get maintainer approval of the proposed resolution
2. ❌ Implement proposed resolution
3. ❌ Test

User interface changes

Changes to the Add User Manual entry form, see above for details.

API changes

None

Data model changes

None