ApplePaySession not working in InAppBrowser

# Bug Report

## Problem

We're using In-App-Browser to open a payment gateway to recieve credit card and Apple Pay payments.
To communicate between the app and the payment gateway we use `iab.executeScript();` and `webkit.messageHandlers.cordova_iab.postMessage()`

**Our code:**
```
showBrowser() {
this.browser = this.iab.create(this.paymentGatewayUrl, '_blank', 'location=no,usewkwebview=yes,hidenavigationbuttons=yes,toolbar=no');
const iapSubscription = this.browser.on('loadstop').subscribe(() => {
this.onInAppBrowserLoadstop();
iapSubscription.unsubscribe();
});
this.browser.show();
}

sendMessage(type: string, message: string) {
let code = 'var message = {type: \'' + type + '\', data: \'' + message + '\'};';
code += 'handleMessage(message)';
this.browser.executeScript({code: code});
}
```

The payment gateway does use `window.ApplePaySession` to check if Apple Pay is available and initiate payments.
But it seems the usage of `executeScript()` does prevent Apple Pay from working. Before using executeScript the function `ApplePaySession.canMakePayments()` is set to true, after it's set to false.

The other way arround, when executing `ApplePaySession.canMakePayments()` first, it seems `iab.executeScript();` is not working anymore.

It's probably a security functionality, but we were not able to find any examples or documentation on this.

### Environment, Platform, Device
Platform is iOS13 on iPhone

### Version information
Ionic:

Ionic CLI : 6.10.1 (C:\Users\morit\AppData\Roaming\npm\node_modules\@ionic\cli)
Ionic Framework : ionic-angular 3.9.9
@ionic/app-scripts : 3.2.4

Cordova:

Cordova CLI : 9.0.0 (cordova-lib@9.0.1)
Cordova Platforms : android 8.1.0
Cordova Plugins : cordova-plugin-inappbrowser 4.0.0, cordova-plugin-ionic 5.4.6, cordova-plugin-ionic-keyboard 2.2.0, cordova-plugin-ionic-webview 4.1.3, (and 14 other plugins)

Utility:

cordova-res (update available: 0.15.1) : 0.13.1
native-run : 1.0.0

System:

NodeJS : v12.16.2 (C:\Program Files\nodejs\node.exe)
npm : 6.14.7

## Checklist

- [x] I searched for existing GitHub issues
- [ ] I updated all Cordova tooling to most recent version
(updated in app browser plugin to latest version)
- [x] I included all the necessary information above

Start with the InAppBrowser executeScript() path and the iOS interaction between ApplePaySession.canMakePayments() and webkit.messageHandlers.cordova_iab.postMessage(). Reproduce the reported ordering on iOS 13, then determine whether the behavior can be fixed or needs documentation explaining the limitation.

Written by the indexing model from the issue text.