Button : deprecate isSmall prop

[t-hamano]

Closes #59733

What?

This PR officially deprecates the isSmall prop of the Button component.

Why?

#51842 introduced size prop, which covers isSmall prop. #53560 also replaced the isSmall prop with the size prop for Button components throughout the Guenberg project. This should allow us to officially deprecate the isSmall prop.

How?

I added an error indicating that a deprecation warning appears from WP6.6 and will be removed in WP6.9. At the same time, I updated types and unit tests.

Testing Instructions

All CIs should be green. Additionally, use the code below to confirm that a console error is displayed when a Button component with the isSmall prop is registered as a custom block.

wp.blocks.registerBlockType( 'test/button-with-is-small', {
	apiVersion: 3,
	title: 'Button with deprecated isSmall prop',
	edit () {
		return wp.element.createElement(
			'div',
			wp.blockEditor. useBlockProps(),
			wp.element.createElement(
				wp.components.Button,
				{ isSmall: true },
				'Push Me',
			),
		);
	},
} );

[github-actions]

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Co-authored-by: t-hamano <wildworks@git.wordpress.org>
Co-authored-by: mirka <0mirka00@git.wordpress.org>
Co-authored-by: tyxla <tyxla@git.wordpress.org>

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[mirka]

I was a bit concerned about the existing deprecation patterns we have in this component, so I'm proposing #59913 to set better conventions for the future. Could you take a look at that please? Then whatever we agree on there, we can integrate those patterns back into this PR.

[mirka]

Suggested change

version: '6.9',

I'm thinking we don't really have to do a hard deprecation on this one, since the maintenance cost is very low. What do you think?

[tyxla]

I think we should start following those more actively and actually clean them all up when they're due. With that in mind, I find them useful and I think they help reduce technical debt over time. scratch that, this comment explained that really well.

[t-hamano]

I updated this PR based on #59913. Perhaps the deprecated warning itself is unnecessary?

[mirka]

Looks good, thank you!

[mirka]

Perhaps the deprecated warning itself is unnecessary?

Yes, I personally don't think it's worth it in this particular case, but I'm not going to block it if you or others think it's warranted. I will suggest adding a Dev Note for the next WP release though.

If we're going to throw a warning, we should add a prefix:

Suggested change

	deprecated( 'Button isSmall prop', {
	deprecated( 'wp.components.Button isSmall prop', {

[t-hamano]

I decided to remove the deprecated() function for now so it doesn't throw any warnings. In the future, we may need to consider adding warnings along with other props such as isPrimary|isTertiary|isSecondary|isLink.