Improve GRPC exception type and message for duplicate instance.

[kaibocai]

Issue describing the changes in this PR

resolves #issue_for_this_pr

We used to get an unclear exception as shown in the above issue. This PR improves the RPCException status and message making it more clear for our customers.

Tested result on Local:

Pull request checklist

• My changes do not require documentation changes
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• My changes should not be added to the release notes for the next release
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  • Otherwise: major or minor version updates are reflected in /src/Worker.Extensions.DurableTask/AssemblyInfo.cs
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  • Otherwise: Ensure the EventIds are within the supported range in our existing Windows infrastructure. You may validate this with a deployed app's telemetry. You may also extend the range by completing a PR such as this one.