feat: keep existing users signed in when moving to native SDK

[DontGiveAFck]

Plugin(s)

• [ ] Analytics
• [ ] App
• [ ] App Check
• [X] Authentication
• [ ] Crashlytics
• [ ] Cloud Firestore
• [ ] Cloud Functions
• [ ] Cloud Messaging
• [ ] Cloud Storage
• [ ] Performance
• [ ] Remote Config

Current problem

Users that were signed in with js sdk in old app version should be kept signed in in new app version that uses native sdk.

Preferred solution

Not sure what exactly should be implemented, maybe signInWithCredential method should help - so we can get token id with js sdk and use it to login with newly implemented signInWithCredential in native sdk

Alternative options

No response

Additional context

No response

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• [X] I have read and followed the feature request guidelines.
• [X] I have attached links to possibly related issues and discussions.