DebugView not working in TestFlight Builds

### Description

We are experiencing the problem, that the Firebase DebugView seems to no longer be working from TestFlight builds.

The documentation states to put the -FIRDebugEnabled param into the scheme launch arguments. This works, but only when starting the app from Xcode. However, for our analytics department and QA, they work with TestFlight builds provided by the devs.

Up until now we were using the following code as a workaround to mutate the launch arguments:

```swift
var args = ProcessInfo.processInfo.arguments
args.append("-FIRAnalyticsDebugEnabled")
args.append("-FIRDebugEnabled")
ProcessInfo.processInfo.setValue(args, forKey: "arguments")
```

As of this thread, this is discouraged and does no longer work: https://forums.developer.apple.com/forums/thread/767584

Therefore we were looking for other solutions and fount two similar issues:

- https://github.com/firebase/firebase-ios-sdk/issues/13598
- https://github.com/firebase/firebase-ios-sdk/issues/13640

The workaround in these issues is supposed to be this:
```swift
UserDefaults.standard.set(true, forKey: "/google/firebase/debug_mode")
UserDefaults.standard.set(true, forKey: "/google/measurement/debug_mode")
```

Turns out, it still did not work for us.

We tested different devices in our company and iOS 16 and 18 did not work under any circumstances. However for two colleagues with iOS 17 devices, the DebugView is still working.

Can you please help on this issue, since this effectively blocks our analytics team from approving tracking in new features.

### Reproducing the issue

_No response_

### Firebase SDK Version

11.5

### Xcode Version

16.1

### Installation Method

Swift Package Manager

### Firebase Product(s)

Analytics, Crashlytics, Messaging

### Targeted Platforms

iOS

### Relevant Log Output

_No response_

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