fix: add support for fiat currency prefixes on NumberDisplay component

[ChefBingbong]

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PR-Codex overview

This PR focuses on restructuring the NumberDisplay components and adding new features like fiat number display formatting.

Detailed summary

• Deleted NumberDisplay/index.tsx
• Added FiatNumberDisplay.tsx
• Added BaseNumberDisplay.tsx
• Updated NumberDisplay.tsx
• Updated formatNumber and formatFiatNumber functions
• Updated packages/widgets-internal/index.ts to include new components

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