[BLOCKING] Can't specify --registry-identity parameter

When creating a container app, you can use the `--registry-identity` parameter to avoid using username/password combination when ACA needs to authenticate with ACR to pull the image to deploy.

As a side benefit, this also sets the User-assigned managed identity that the container app will use, which is key to let the container app access several other Azure resources without the need for connection strings or any sort of API keys.

However, I can't find a way to specify the `--registry-identity` parameter with the `AzureContainerAppsRC` task.

As a workaround, I tried injecting the missing parameter into the ingress parameter, which is very hacky:

```yaml
- job: Deploy

variables:
acrName: '[MYACR]'
registryIdentity: '/subscriptions/[SUBSCRIPTIONID]/resourcegroups/[RESOURCE GROUP]/providers/Microsoft.ManagedIdentity/userAssignedIdentities/mi-sfa5ktnjiw4d4'

steps:
- task: AzureContainerAppsRC@1
displayName: 'Deploy to ACA'
inputs:
azureSubscription: 'Azure Sponsorship'
imageToDeploy: '$(acrName).azurecr.io/catalog-service:$(Build.BuildNumber)'
containerAppName: 'catalog-service'
resourceGroup: 'rg-gamestore02'
ingress: 'internal --registry-server $(acrName).azurecr.io --registry-identity $(registryIdentity)'
acrName: '$(acrName)'
```

But this only works during initial app creation, not for subsequent updates, where the task fails due to it trying to update the ingress.

The command executed by the task:

```bash
az containerapp create -n catalog-service -g [RESOURCE GROUP] -i [MYACR].azurecr.io/catalog-service:1.0.33 --environment cae-sfa5ktnjiw4d4 --ingress internal --registry-server [MYACR].azurecr.io --registry-identity /subscriptions/[SUBSCRIPTIONID]/resourcegroups/[RESOURCE GROUP]/providers/Microsoft.ManagedIdentity/userAssignedIdentities/mi-sfa5ktnjiw4d4 --target-port 8080
```

Can we either add support for the `--registry-identity` argument or just add an `extraArguments` argument where I can add any other desired arguments?

Also, notice that when specifying `--registry-identity` you also need to specify `--registry-server`, or it won't work.

Start by locating the AzureContainerAppsRC task entry point and the code that builds the az containerapp create and update arguments, then inspect how ingress options are handled. Done means the task accepts registry identity together with registry server, works for both initial creation and subsequent updates, and preserves the existing deployment behavior.

Written by the indexing model from the issue text.