Grid resize better handles

[ruggi]

Problem:

The resize grid strategy has some UI issues:

1. the handles are only shown when a grid cell is selected, not the grid itself
2. the handles are not positioned correctly relatively to the grid itself
3. it's hard to discern precisely the resize effects

Fix:

1. Enable the grid resizing if the grid is selected too
2. Position the handles centered relatively to the grid rows/columns
3. Replace the "numbered handles" with more subtle draggable circles
4. During drag, show a striped background for the affected row or column, with the measurements centered in the striped area

Note
The handles icons are placeholders/ideas.

Before	After

[github-actions]

Try me

[relativeci]

#13316 Bundle Size — 62.62MiB (~+0.01%).

3b6200f(current) vs 6339ece master#13302(baseline)

Warning

Bundle contains 51 duplicate packages – View duplicate packages

Bundle metrics   2 changes 1 regression

	Current #13316	Baseline #13302
Initial JS	45.68MiB(~+0.01%)	45.67MiB
Initial CSS	0B	0B
Cache Invalidation	21.62%	21.58%
Chunks	30	30
Assets	33	33
Modules	4350	4350
Duplicate Modules	524	524
Duplicate Code	31.71%	31.71%
Packages	450	450
Duplicate Packages	51	51

Bundle size by type   2 changes 1 regression 1 improvement

	Current #13316	Baseline #13302
JS	62.61MiB (~+0.01%)	62.61MiB
HTML	11.16KiB (-0.33%)	11.2KiB

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