Enable running tests on different AAD tenant (microsoft#668)

### Motivation and Context
It can be hard running integration tests when one does not have admin
permissions in one's tenant.

### Description
Add possibility to use a different (test) tenant to facilitate testing
of CC.

### Contribution Checklist
- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [Contribution
Guidelines](https://github.com/microsoft/chat-copilot/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/chat-copilot/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

.github/workflows/copilot-deploy-infra.yml

@@ -59,4 +59,6 @@ jobs:
           inlineScript: |
             AI_SERVICE_KEY=$(az cognitiveservices account keys list --name ${{vars.AZUREOPENAI__NAME}} --resource-group ${{vars.AZUREOPENAI_DEPLOYMENT_GROUP_NAME}} | jq -r '.key1')
             echo "::add-mask::$AI_SERVICE_KEY"
-            scripts/deploy/deploy-azure.sh --subscription ${{secrets.AZURE_SUBSCRIPTION_ID}} --resource-group ${{vars.CC_DEPLOYMENT_GROUP_NAME}} --deployment-name ${{steps.deployment-id.outputs.deployment_name}} --region ${{vars.CC_DEPLOYMENT_REGION}} --client-id ${{vars.BACKEND_CLIENT_ID}} --frontend-client-id ${{vars.APPLICATION_CLIENT_ID}} --tenant-id ${{secrets.AZURE_TENANT_ID}} --instance ${{vars.AZURE_INSTANCE}} --ai-service AzureOpenAI --ai-endpoint ${{secrets.AZURE_OPENAI_ENDPOINT}} --ai-service-key $AI_SERVICE_KEY --app-service-sku ${{vars.WEBAPP_API_SKU}} --no-deploy-package --debug-deployment --deploy-web-searcher-plugin
+            APP_TENANT_ID=${{vars.APPLICATION_TENANT_ID}}
+            [  -z "$APP_TENANT_ID" ] && APP_TENANT_ID=${{secrets.AZURE_TENANT_ID}} # Use secrets.AZURE_TENANT_ID if vars.APPLICATION_TENANT_ID is not set
+            scripts/deploy/deploy-azure.sh --subscription ${{secrets.AZURE_SUBSCRIPTION_ID}} --resource-group ${{vars.CC_DEPLOYMENT_GROUP_NAME}} --deployment-name ${{steps.deployment-id.outputs.deployment_name}} --region ${{vars.CC_DEPLOYMENT_REGION}} --client-id ${{vars.BACKEND_CLIENT_ID}} --frontend-client-id ${{vars.APPLICATION_CLIENT_ID}} --tenant-id $APP_TENANT_ID --instance ${{vars.AZURE_INSTANCE}} --ai-service AzureOpenAI --ai-endpoint ${{secrets.AZURE_OPENAI_ENDPOINT}} --ai-service-key $AI_SERVICE_KEY --app-service-sku ${{vars.WEBAPP_API_SKU}} --no-deploy-package --debug-deployment --deploy-web-searcher-plugin

.github/workflows/copilot-run-integration-tests.yml

@@ -1,6 +1,7 @@
 name: copilot-run-integration-tests
 
 on:
+  workflow_dispatch:
   workflow_call:
     inputs:
       ENVIRONMENT: