Fix authStateChanged after app is reloaded (fixes #1677)

[ghsdh3409]

Summary

• It closes onAuthStateChanged not returning any result on iOS Sumulator #1677.
• onAuthStateChanged sometimes is not fired after app is reloaded on iOS.
  • I checked it on v5.1.0.
• I found followings on debugging.
  • When the app is reloaded, dealloc sometimes is not called. So, deallocation task does not work.
  • iOS native callback addAuthStateDidChangeListener works well.
  • emitter.bridge is null when JS onAuthStateChanged is not fired.
• I added deallocation task using RCTInvalidating.
  • ref: https://stackoverflow.com/a/38161889

Checklist

• Supports Android
• Supports iOS
• e2e tests added or updated in /tests/e2e/*
• Updated the documentation in the docs repo
  • LINK TO DOCS PR HERE
• Flow types updated
• Typescript types updated

Test Plan

• How to reproduce
  • onAuthStateChanged not returning any result on iOS Sumulator #1677 (comment)

Release Plan

[IOS][BUGFIX] [FirebaseModule] - Fix authStateChanged is not called after app is reloaded

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[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #1698 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1698   +/-   ##
=======================================
  Coverage   75.88%   75.88%           
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  Files          72       72           
  Lines        1837     1837           
=======================================
  Hits         1394     1394           
  Misses        443      443

[Ehesp]

@ghsdh3409 Thanks very much for this. Could you approve the CLA?

[ghsdh3409]

@Ehesp
Thanks for letting me know! I approved!

[Salakar]

@ghsdh3409 thanks for debugging and fixing this 🎉