Detect and provide warning for usage of "/providers/" in the type string

[anthony-c-martin]

The pattern of formatting type strings using "/providers/" is very pervasive in ARM template samples, so it would be great if we could provide a guiding error message on how to use the "scope" property instead to declare extension resources (with a documentation link).

As far as I'm aware, '/providers/' is reserved in ARM, and RPs cannot use it to declare a genuine resource type, so this feels safe. Something to confirm, of course.

As an example:

resource 'Microsoft.ContainerRegistry/registries/providers/roleAssignments' = {
//                                               ~~~~~~~~~ we should be able to warn about this
  ...
}

Should be replaced by the following (where registry is a reference to a new or existing Microsoft.ContainerRegistry/registries resource):

resource 'Microsoft.Authorization/roleAssignments' = {
  scope: registry
  ...
}

Some examples of confusion this could help prevent:
#784 (comment)
#784 (comment)
#784 (comment)
#784 (comment)
#784 (comment)
#1936
#1935
#1703

[alex-frankel]

Seems like a good use of the linter cc @MarcusFelling @jfleisher

[anthony-c-martin]

Seems like a good use of the linter cc @MarcusFelling @jfleisher

I've already got the fix PR out as I'm keen to get it into the upcoming release to stop the confusion. Definitely open to moving this into the linter out in the future however.