Add support for column and row spans in grid children.

[tellthemachines]

Trac ticket: https://core.trac.wordpress.org/ticket/61111

Syncs the changes from https://github.com/WordPress/gutenberg/pull/58539, https://github.com/WordPress/gutenberg/pull/59057 and https://github.com/WordPress/gutenberg/pull/59452 to core.

To test, paste the following markup in a post:

test markup

<!-- wp:group {"layout":{"type":"grid"}} -->
<div class="wp-block-group"><!-- wp:paragraph {"style":{"color":{"background":"#91ded8"},"layout":{"columnSpan":"2"}}} -->
<p class="has-background" style="background-color:#91ded8">grid item</p>
<!-- /wp:paragraph -->

<!-- wp:paragraph {"style":{"color":{"background":"#91ded8"},"layout":{"rowSpan":"3"}}} -->
<p class="has-background" style="background-color:#91ded8">grid item</p>
<!-- /wp:paragraph -->

<!-- wp:paragraph {"style":{"color":{"background":"#91ded8"}}} -->
<p class="has-background" style="background-color:#91ded8">grid item</p>
<!-- /wp:paragraph -->

<!-- wp:paragraph {"style":{"color":{"background":"#91ded8"}}} -->
<p class="has-background" style="background-color:#91ded8">grid item</p>
<!-- /wp:paragraph -->

<!-- wp:paragraph {"style":{"color":{"background":"#91ded8"}}} -->
<p class="has-background" style="background-color:#91ded8">grid item</p>
<!-- /wp:paragraph -->

<!-- wp:paragraph {"style":{"color":{"background":"#91ded8"}}} -->
<p class="has-background" style="background-color:#91ded8">grid item</p>
<!-- /wp:paragraph --></div>
<!-- /wp:group -->

Save and view on the front end. It should show grid items spanning multiple columns and rows:

Todo: add tests.

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions[bot]]

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[github-actions[bot]]

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Core Committers: Use this line as a base for the props when committing in SVN:

Props isabel_brison, andrewserong, peterwilsoncc, mukesh27.

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[tellthemachines]

I've added a test so marking this one ready for review!

[tellthemachines]

Committed in r58170.