CodeGen from PR 16463 in Azure/azure-rest-api-specs

Add 2021-05-01-preview swagger API support for Autoscale newly added fields and new controller path. (#16463)

* Initially cut, cloned from know existing GA bits (IE \specification\monitor\resource-manager\Microsoft.Insights\stable\2015-04-01)

* rev API version, add new controller API path, and update JSON showing newly added predictiveAutoscalePolicy field

Author: SDKAuto