Grid resize: remove shorthand, serialize other longhand when not auto

[ruggi]

Problem:

If a grid is configured with the gridTemplate shorthand, resizing the grid does not handle that correctly.

Fix:

This PR handles gridTemplate shorthands during template changes via the canvas.
An incremental PR will do the same for the inspector template editing.

For example, if a grid is configured as follows: gridTemplate: 1fr 2fr / 3fr 4fr, changing its first column to 3.5fr will result in the following style:

gridTemplateColumns: '3.5fr 4fr',
gridTemplateRows: '1fr 2fr'

If a grid has a shorthand with an axis being the default (a single auto keyword), for example gridTemplate: auto / 3fr 4fr, the same change as above will result in:

gridTemplateColumns: '3.5fr 4fr',

Fixes #6580

[github-actions]

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[relativeci]

#14909 Bundle Size — 57.98MiB (~+0.01%).

60150e4(current) vs 916e8b9 master#14908(baseline)

Warning

Bundle contains 70 duplicate packages – View duplicate packages

Bundle metrics   3 changes 1 regression

	Current #14909	Baseline #14908
Initial JS	40.96MiB(~+0.01%)	40.96MiB
Initial CSS	0B	0B
Cache Invalidation	17.99%	0%
Chunks	20	20
Assets	22	22
Modules	4152	4152
Duplicate Modules	213	213
Duplicate Code	27.33%(-0.04%)	27.34%
Packages	477	477
Duplicate Packages	70	70

Bundle size by type   2 changes 1 regression 1 improvement

	Current #14909	Baseline #14908
JS	57.97MiB (~+0.01%)	57.97MiB
HTML	7.37KiB (-0.25%)	7.39KiB

Bundle analysis report Branch feat/grid-resize-shorthand-handl... Project dashboard

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