CodeGen from PR 15636 in Azure/azure-rest-api-specs

[Hub Generated] Review request for Microsoft.Insights to add version preview/2018-05-01-preview (#15636)

* 2018-05-01-preview

* change version

* delete file added by mistake

* fix version of examples

* reference webTests_API in readme

Co-authored-by: Gustavo Lima <guslima@microsoft.com>

Author: SDKAuto