support x-ms-azure-rbac-permissions-required

[pshao25]

Here is the spec link: https://github.com/Azure/azure-rest-api-specs/blob/5b041764f26fcff04fbc00cacef378730f1d2bda/specification/authorization/resource-manager/Microsoft.Authorization/Authorization/stable/2015-07-01/authorization-ElevateAccessCalls.json#L60-L67

[markcowl]

As far as I can tell, this appears exactly one time in one spec, so it can't possibly be widely used by consumers of swagger. Most likely we can just ignore it. If we decide for some reason that we need to have it in swagger, using the openapi extension should be a perfectly acceptable way to represent it.

[markcowl]

Instances of this extension: https://github.com/search?q=repo%3AAzure%2Fazure-rest-api-specs%20x-ms-azure-rbac-permissions&type=code