When emulators don't launch the return code should always be non-zero

This has been mentioned in some other issues (did not find them..), but still remains at least for this one case.

**Expected behavior**

Whenever there is an error in launching Emulators that causes them to **not** launch, the `firebase emulators:start` command should return with a **non-zero** return code.

This is normal Unix tool behaviour.

**Actual**

With certain errors, `firebase emulators:start` prints an error message but return with a zero return code.

The example is from Docker Compose. If I map things wrong, `firestore-debug.log` is a directory, instead of a file. This confuses the emulators to:

```
Step #2: emul | Launching Docker... 🐳
Step #2: emul | i emulators: Starting emulators: functions, firestore, database
Step #2: emul | ✔ functions: Using node@16 from host.
Step #2: emul | i firestore: Firestore Emulator logging to firestore-debug.log
Step #2: emul |
Step #2: emul | Error: An unexpected error has occurred.
Step #2: emul exited with code 0
```

Note the "exited with code 0".

### [REQUIRED] Environment info

- `firebase-tools` 11.2.1
- Platform: Cloud Build

### [REQUIRED] Test case

- Have an otherwise working Firebase Emulators project
- Create a folder `firebase-debug.log`
- Launch the emulators

At exit, `echo $?` to see the return code.

### [REQUIRED] Expected behavior

If the emulators don't start, `firebase` should return with non-zero code.

### [REQUIRED] Steps to reproduce

see `Test case`

### [REQUIRED] Actual behavior

At least in the above case, it returns with 0.

I wish you have the time to look through the code for any such cases.