auth.createCustomToken: Failed to determine service account. Make sure to initialize the SDK with a service account

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### [REQUIRED] Step 2: Describe your environment

* Operating System version: Windows 11 24H2
* Firebase SDK version: 13.4.0
* Firebase Product: Firestore
* Node.js version: 21.6.1
* NPM version: 10.2.4

### [REQUIRED] Step 3: Describe the problem

Basically duplicates [2800](https://github.com/firebase/firebase-admin-node/issues/2800)

#### Steps to reproduce:

Running Firebase Functions emulator on local environment
```typescript
import { initializeApp } from "firebase-admin/app"

initializeApp()
```

#### Relevant Code:

```typescript
const token = await auth.createCustomToken(uid, customClaims)
```

This throws

>Failed to determine service account. Make sure to initialize the SDK with a service account credential. Alternatively specify a service account with iam.serviceAccounts.signBlob permission. Original error: Error: Error while making request: getaddrinfo ENOTFOUND metadata.

And I have to do
```typescript
export const json_path = 'LOCAL_PATH'

getApps().length === 0
? initializeApp({
credential: credential.cert(json_path!),
})
: getApp()
```
Which also does not work with ADC file, only with json downloaded from project settings in Firebase dashboard. If I put ADC file path in the snippet above, it complains about project_id field missing. It definitely worked with simply initializeApp() before upgrading to v13.