Firebase visionOS CocoaPods support

[nevil]

This seems to be resolved since CocoaPods 1.15.0
https://github.com/CocoaPods/CocoaPods/releases/tag/1.15.0

          CocoaPods support is [not yet fully implemented](https://github.com/CocoaPods/CocoaPods/issues/12118) and Firebase's initial support is only available via Swift Package Manager.

Originally posted by @paulb777 in #11890 (comment)

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[paulb777]

Given the multiple open issues that remain on CocoaPods for visionOS, we're not yet ready to prioritize.

In the meantime, please thumbs-up the issue to indicate interest.