Improve ZIP handling and compatibility with upload pipeline

[VanshikaSabharwal]

Description

• This PR updates the ZIP utility to ensure compatibility with the deployment/upload pipeline by converting the archiver output into a Blob instead of returning the Archiver instance directly.

Changes I made:-

• Collect ZIP data chunks from archiver stream using data event
• Concatenate chunks into a single Buffer
• Return a Blob (application/x-zip-compressed) instead of Archiver
• Added explanatory comment about why Archiver cannot be used directly

Reason:-
The archiver package does not return a native Node.js Readable stream. Instead, it extends readable-stream's Transform, which causes issues when passing it to the deployment protocol (e.g., instanceof Readable checks fail).

This resulted in incompatibility with the upload mechanism.

By buffering the archive output and returning it as a Blob, we ensure:

• Compatibility with the existing upload pipeline
• Avoidance of stream-type mismatches
• Consistent behavior across environments

Working GitHub workflow Link:- https://github.com/VanshikaSabharwal/faas/actions/runs/24439286633/job/71400355463