Microsoft.ApiManagement/service/workspaces/apis/policies: "name" has to be equal to "policy"

### Resource Type

Microsoft.ApiManagement/service/workspaces/apis/policies

### Api Version

2023-03-01-preview

### Issue Type

Confusing error message on deployment

### Other Notes

When I try to deploy a policy with bicep it just throws:

```
[{"code":"BadRequest","message":""}]
```

After a lot of trial and error I got it working after changing the "name" property to "policy". I can't imagine this being intended. If it is please provide a more accurate error message.

### Bicep Repro

resource policy 'Microsoft.ApiManagement/service/workspaces/apis/policies@2023-03-01-preview' = {
name: 'anyNameOtherThanPolicyFails'
parent: api
properties: {
value: loadTextContent('jwt-policy.xml')
format: 'rawxml'
}
}

### Confirm

- [X] I have read the troubleshooting guide and looked for duplicates.

Start by locating the TypeScript definition for Microsoft.ApiManagement/service/workspaces/apis/policies at API version 2023-03-01-preview, then reproduce the deployment using the Bicep example and its policy resource name. Determine whether the definition documents or validates the required name; done means the restriction is accurately represented or the deployment reports a useful error.

Written by the indexing model from the issue text.