Refactor the Merged MR widgets lower area to single component

What does this MR do and why?

For #353615 (closed).

• Blends the existing subtext for some widgets into the lower area
• Removes some lower area text in those cases

Rather than trying to toggle lines of text on and off based on

• a feature flag,
• which component is displaying elsewhere, and
• a fairly large collection of booleans,

...this MR refactors those things into a single component for the Merged state.

Now, when the feature flag is on, and the Merged state is displaying, a single component is rendered that handles all of the gray "well" subtext.

MR	Description
This MR	Restructures (again) the restructured MR Widget for the Merged state
!82844 (merged)	A bug identified in the Original Restructured MR Widget (which is still feature flagged), that uses a non-existent CSS class.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the restructured_mr_widget feature flag
2. View a merged MR

MR acceptance checklist

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