Include required RBAC Action(s) for each operation in documentation

See [Azure PowerShell Issue 6843](https://github.com/Azure/azure-powershell/issues/6843)

There are many scenarios where to perform a given operation, there isn't a least-privileged built-in RBAC role that grants the required permissions to perform the operation. Simple examples include restarting a Web App, VM, etc. Other scenarios (which are more complex beyond the rest apis themselves) include granting SQL DB Contributor on a SQL DB doesn't actually allow you to run an ARM deployment as that also requires Microsoft.Resources/deployments/* on the instance's resource group.

Please consider documenting the required RBAC actions per operation so that it is easier to discover and determine when it is appropriate for creating a custom RBAC role.

No file, test, or entry point is identified. Start by reviewing the Azure REST API specifications and the linked Azure PowerShell issue to define the documentation scope; done means required RBAC actions are documented for each operation and the guidance covers custom-role decisions.

Written by the indexing model from the issue text.