Use banned functions to suggest why certain functions are unsupported at certain scopes

[anthony-c-martin]

Example repro here.

targetScope = 'tenant'

// this is blocked, but the error message could be clearer
var myResGroup = resourceGroup('abc', 'def')

[majastrz]

Btw, it occurs to me that we can emulate banned overloads by conditionally setting the return type of a particular overload to an error type with the appropriate error message.

[anthony-c-martin]

This is no longer repro-able following #1339