Use linked templates for deployment

It will make the ARM template much more readable & reusable.

Also, use the `copy()` function to deploy the App Services and split the `appSettings` and other `config` stuff from the App Service deployment template.

Locate the ARM deployment template and review how App Services, appSettings, and other configuration are currently defined. Refactor the deployment into linked templates, use copy() for App Services, and separate configuration from the App Service deployment; verify that the deployment remains valid.

Written by the indexing model from the issue text.