Inconsistent paddings/margins for dashboard widgets

[johnjamesjacoby]

This seems related to #64787 and #64549, but there are a few weird visual inconsistencies in trunk related to dragging & dropping meta-boxes in the dashboard pages:

• Unique & low-contrast drop-zone background color, which also shows off the bottom padding in an unflattering way
• Two different border dash styles (not new but doesn't seem that useful anymore IMO)
• Drop-zones have different spacing when they are vacant or populated
• Dragging a meta-box out of bounds causes it to be clipped (overflow hidden?)

[johnjamesjacoby]

Clipped while dragging

## Summary

• normalize dashboard widget drop-zone outlines while dragging
• reduce the oversized empty-column spacing so vacant and populated columns feel more consistent
• allow dragged dashboard widgets to extend beyond the wrapper without being clipped

## Testing Instructions

1. Open /wp-admin/index.php on a wide desktop viewport so the Dashboard uses multiple columns.
2. Ensure there is an empty dashboard widget column.
3. Drag a widget into and across the empty column.
4. Confirm the drop zones use consistent dashed outlines, the vacant column spacing feels closer to populated columns, and the dragged widget is not clipped while moving.

Closing this draft in favor of a replacement PR from the renamed branch .

## Summary

• normalize dashboard widget drop-zone outlines while dragging
• reduce the oversized empty-column spacing so vacant and populated columns feel more consistent
• allow dragged dashboard widgets to extend beyond the wrapper without being clipped

## Testing Instructions

1. Open /wp-admin/index.php on a wide desktop viewport so the Dashboard uses multiple columns.
2. Ensure there is an empty dashboard widget column.
3. Drag a widget into and across the empty column.
4. Confirm the drop zones use consistent dashed outlines, the vacant column spacing feels closer to populated columns, and the dragged widget is not clipped while moving.

[audrasjb]

Removing trunk version as this is not going to be shipped with WP 7.0 but in the next releases.