Button API alignment

[langermank]

This PR includes breaking changes to bring the PRC Button up to the agreed upon API spec and match implementation with PVC.

• Changes leadingIcon and trailingIcon to leadingVisual and trailingVisual (a pattern introduced with ActionList)
• Removes Button.Counter as a child component, replacing it with a trailingVisualCount prop. This change allows us to use the trailingVisual slot for counters, and also aligns better with all the other child elements within Button (visuals are props, not child components in this case.)
• Removes the outline button variant as we wish to only support invisible buttons.

Screenshots

The only visual change is that the outline button variant has been removed.

Merge checklist

• Added/updated tests
• Added/updated documentation
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

[changeset-bot]

🦋 Changeset detected

Latest commit: 674e54d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Major

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[github-actions]

size-limit report 📦

Path	Size
dist/browser.esm.js	84.75 KB (-0.19% 🔽)
dist/browser.umd.js	85.35 KB (-0.2% 🔽)

[joshblack]

Hey @langermank! I've been trying to make sure all the branches are up-to-date with the new vrt workflow. I wanted to ask if you have any free time this week to update the conflicts on this PR?

[langermank]

@joshblack thanks for the reminder! I'm waiting for this PR that @broccolinisoup is working with me on to land before I update this PR since I think it will resolve a lot of the conflicts here. I had to revert the original PR that this PR is based on.

[langermank]

Will reopen once #2792 merges

[langermank]

Note to self: add these changes to this PR d79fbfc