feat(firestore): add support for onSnapshotsInSync

[SelaseKay]

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Description

Currently the firebase-js-sdk has an onSnapshotsInSync API and react-native-firebase does not

This PR (when complete) will close that feature gap)

Related issues

Release Summary

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • [ ] Yes
• My change supports the following platforms;
  • [ ] Android
  • [ ] iOS
  • [ ] Other (macOS, web)
• My change includes tests;
  • [ ] e2e tests added or updated in packages/\*\*/e2e
  • [ ] jest tests added or updated in packages/\*\*/__tests__
• [ ] I have updated TypeScript types that are affected by my change.
• This is a breaking change;
  • [ ] Yes
  • [ ] No

Test Plan

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