feat(e2e): Updated readme with setup instructions (Azure#16583)

Author: vinagesh

sdk/digitaltwins/Azure.DigitalTwins.Core/tests/prerequisites/generateArmTemplate.ps1

@@ -0,0 +1,2 @@
+$bicepFile = Join-Path -Path $PSScriptRoot -ChildPath "../../../test-resources.bicep"
+bicep build $bicepFile

sdk/digitaltwins/Azure.DigitalTwins.Core/tests/prerequisites/prerequisite readme.md

@@ -1,7 +1,5 @@
 # Prerequisites
 
-## Install
-
 ### Install the latest Powershell 7
 
 - Make sure you run the script using the latest stable version of [powershell 7](https://github.com/PowerShell/PowerShell/releases)
@@ -13,13 +11,23 @@
   - If it isn't, update it
 - Use this link to install [Azure CLI](https://docs.microsoft.com/cli/azure/install-azure-cli?view=azure-cli-latest])
 
-## Delete
+### Install Bicep
+
+- Install using the instructions in [bicep](https://github.com/Azure/bicep/blob/main/docs/installing.md)
+
+### Run the setup script
+
+The script outputs [test-resources.bicep](https://github.com/Azure/azure-sdk-for-net/blob/master/sdk/digitaltwins/test-resources.bicep) file in the root folder [digitaltwins](https://github.com/Azure/azure-sdk-for-net/tree/master/sdk/digitaltwins)
+
+- `.\setup.ps1`
+
+### Generate the ARM template
+
+The ARM template [test-resources.json](https://github.com/Azure/azure-sdk-for-net/blob/master/sdk/digitaltwins/test-resources.json) is generated from the [test-resources.bicep](https://github.com/Azure/azure-sdk-for-net/blob/master/sdk/digitaltwins/test-resources.bicep) file by running the following script
 
-To delete the digital twins instance, you need to first delete the endpoint added by the script (the service doesn't yet support cascading delete).
+- `.\generateArmTemplate.ps1`
 
-1. To do this, run the command `az dt endpoint delete -n <dt name> -g <rg name> --en someEventHubEndpoint`.
-1. If you have other endpoints that have been added outside this script, you can discover them with the command `az dt endpoint list -n <dt name> -g <rg name>`.
-1. Then delete them with the same command in step 1.
+> **Note**: Do not update the ARM template (test-resources.json) manually. Any changes should be made only to the test-resources.bicep file and the ARM template (test-resources.json) should be generated using the above command.
 
 ## Maintenance