[#522] Replace Firebase Token with Google Service Account

[blyscuit]

• Close Replace Firebase Token with Google Service Account #522

What happened 👀

• Replace FIREBASE_TOKEN from all workflows Secrets and use FIREBASE_GOOGLE_APPLICATION_CREDENTIALS instead.

Insight 📝

• Update test workflow to use FIREBASE_GOOGLE_APPLICATION_CREDENTIALS as well.
• Not sure for CodeMagic and Bitrise
  • For CodeMagic, I used this document.
  • For Bitrise it seems to be passable from the file upload section. https://devcenter.bitrise.io/en/connectivity/connecting-to-services/connecting-a-google-service-account-to-bitrise.html. There is no FIREBASE_TOKEN declared in the current Bitrise.yml so I didn't change it.

Proof Of Work 📹

Firebase test workflow works.