Support loading bundled sog from request

[slimbuck]

Description

Update the bundled SOG loader to use the same asset interface as PLY.

User can provide URL, fetch request or arrayBuffer.

Also emit progress events like ply and unbundled SOG.

Fixes playcanvas/supersplat-viewer#66

[Copilot]

Pull Request Overview

Updates the bundled SOG loader to support multiple input types (URL, fetch request, or ArrayBuffer) and adds progress event emission, aligning with the PLY loader's asset interface.

• Refactored the load method to use async/await instead of callback-based asset fetching
• Added downloadArrayBuffer function to handle different input types and emit progress events
• Removed dependency on Asset.fetchArrayBuffer in favor of custom download logic

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