chore: make ReactNativeFirebaseMessagingSerializer + events builder functions public

[alexisbronchart]

Description

I am in a situation where I need to manually send events through ReactNativeFirebaseEventEmitter. See discussion #4577
In order to properly do so, I'd like to use the functions present in ReactNativeFirebaseMessagingSerializer.
This PR just adds the public access modifier to that class and to the functions that build events.

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • Yes
• My change supports the following platforms;
  • Android
  • iOS
• 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

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All committers have signed the CLA.

[codecov]

Codecov Report

Merging #4618 (ea972e7) into master (bda2d67) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4618      +/-   ##
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- Coverage   85.42%   85.37%   -0.05%     
==========================================
  Files         109      109              
  Lines        3710     3710              
  Branches      346      346              
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- Hits         3169     3167       -2     
- Misses        476      478       +2     
  Partials       65       65              

[mikehardy]

We have some history of doing this in Firebase classes, and this follows the exact precedent

We may be slightly less careful with regards to breaking changes coming through as this now represents public API surface area that is not normal for us to consider but we'll try to semver those correctly too (if they ever change, unlikely, but just a heads up - it'll be a compile-time thing anyway so will fail fast even if we mess up semver here)

So these LGTM

[mikehardy]

I have a medium-size stack of changes pending release now, plus some CI work to do, which is to say that I'm expecting to release these shortly (I want to get that stack out...) but it may take a day or three (the CI work is also important prior to release, there are a couple things not working well and I don't want to have a quality error). So please have patience but also you can click the "patch package" CI check from this PR run and you'll find an artifact associated with that CI check. It has the official patch-package files you can use in the meantime, knowing that they'll match the future release exactly so you don't have to wait on me

Cheers

[mikehardy]

CI triage / fix completed in #4600 - this should be good to go