[FR] Add check to verify if auth emulator host is valid

[amalej]

Is your feature request related to a problem? Please describe. I accidentally used http://127.0.0.1:9099 instead of 127.0.0.1:9099 when setting FIREBASE_AUTH_EMULATOR_HOST.

Even though the emulator thew an error like below, it still took me a while to figure out what I did wrong 🤦 :

FirebaseAppError: Error while making request: getaddrinfo ENOTFOUND http. Error code: ENOTFOUND
    at C:\Users\PATH\firebase-admin-node\lib\utils\api-request.js:268:19
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async main (file:///C:/Users/PATH/auth.js:12:5) {
  errorInfo: {
    code: 'app/network-error',
    message: 'Error while making request: getaddrinfo ENOTFOUND http. Error code: ENOTFOUND'
  },
  codePrefix: 'app'
}

Describe the solution you'd like Throw an error message indicating that http and https should not be included when setting FIREBASE_AUTH_EMULATOR_HOST. Found a similar logic in https://github.com/firebase/firebase-admin-node/blob/a46086b61f58f07426a6ca103e00385ae216691d/src/storage/storage.ts#L51-L56

Describe alternatives you've considered N/A

Additional context N/A

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