[MR Widget Restructure] Merging: Show merge details in lower area
Problem
The Merging
state MR Widget is still showing the pre-merge state in its lower half (including form controls, buttons, etc.).

Target
The Merging
state should look like the Figma design:

Notes
There are two steps that need to happen here:
- Show the
Merge Details
section instead of the "Ready to Merge" controls. - Move the second line of text from the top section into the Merge Details section.