Bug: Unable to import any resources from Insights version 2021-05-01-preview

[theunrepentantgeek]

Describe the bug

When trying to import a new resource from Microsoft.Insights, the Load Types stage of the generator crashes with a panic. This is the error from the start of the panic (formatted for readability):

error generating code: 
failed to execute stage 1: Load all types from Swagger files: 
panic: 
While merging file /workspaces/azure-service-operator/v2/specs/azure-rest-api-specs/specification/monitor/resource-manager/Microsoft.Insights/preview/2021-05-01-preview/subscriptionDiagnosticsSettings_API.json: 
duplicate resource types generated

To Reproduce

Add this to the objectModelConfiguration section for insights:

    2021-05-01-preview:
      DiagnosticSetting:
        $export: true
        $supportedFrom: v2.10.0

Also add this to the typeFilters (to allow the new preview version to be seen):

  - action: include
    group: insights
    version: v*20210501preview
    because: We're using DiagnosticSetting from this.

Expected behavior

The specified resource should be imported.

If any error occurs, the error message should be useful to an end user.

Additional context

Error reported via Slack.