[button] add xl and large button sizes

[laurenmrice]

1. Add xl (80px) and large (64px) sizes for theses button component types:
   *These sizes do not apply to icon only buttons.

• Primary
• Secondary
• Tertiary
• Ghost
• Danger

2. Add xl (80px) option to the modal component in the pieces section for the button and footer symbols.

Ref issue: carbon-design-system/carbon#7003

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• White theme
• Gray 10 theme
• Gray 90 theme
• Gray 100 theme

[stale]

We've marked this issue as stale because there hasn't been any activity for a couple of weeks. If there's no further activity on this issue in the next three days then we'll close it. You can keep the conversation going with just a short comment. Thanks for your contributions.

[stale]

We've marked this issue as stale because there hasn't been any activity for a couple of weeks. If there's no further activity on this issue in the next three days then we'll close it. You can keep the conversation going with just a short comment. Thanks for your contributions.

[jillianhowarth]

Added the large and xl buttons to all four kits. These will be available in the next update 🎉
Guidance for when to use these buttons needs to be added to the button usage docs (#2218)