feature(ui): Implement socialButtonsPlacement layout logic

[alexcarpenter]

Description

Implements socialButtonsPlacement logic.

Example:

<SignIn
  appearance={{
    layout: {
      socialButtonsPlacement: 'bottom',
    },
  }}
/>

Top	Bottom

Closes SDKI-559

Checklist

• npm test runs as expected.
• npm run build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other:

[changeset-bot]

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Latest commit: 97a91ae

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