Redeploy an bicep deployment, which contains an APP-GW results in deleting the existing backend pools, listeners and rules

**Bicep version**
Bicep CLI version 0.3.255 (589f0375df)

**Describe the bug**
TL;DR: Redeploy an bicep deployment, which contains an APP-GW results in deleting the existing backend pools, listeners and rules

We use the azure application gateway ingress controller for our AKS cluster. Depending on the workload and deployed Ingress it will automatically creats the backend pool/listeners and rules in the Application Gateway.

Wen we redeploy the bicep scripts, these existing backend pools, listeners and rules gets deleted and the defaults get created again (you can not deploy an applicaton gatway empty...)

Is there a way to preserve existing backend pools, listeners and rules, when redeploying the bicep script?

**To Reproduce**
Follow https://github.com/Azure/application-gateway-kubernetes-ingress/blob/master/docs/setup/install-new.md and redeploy the bicep script, which contains the APP-GW.

Start by following the linked application-gateway-kubernetes-ingress installation guide and redeploying the Bicep script that contains the Application Gateway. Compare the gateway's backend pools, listeners, and rules before and after redeployment. Done means existing controller-created configuration is preserved while the deployment still succeeds.

Written by the indexing model from the issue text.