#14325 [csharp] - Add CancellationToken to generated aspnetcore controller methods.

Created by: philkild

Resolve #14325 (closed). The change adds a CancellationToken to all generated aspnetcore controller methods. The change can be verified by updating /bin/configs/aspnetcore-3.0.yaml with the below and generating the samples. Without these settings, the generated samples are unchanged:

  operationIsAsync: true
  operationResultTask: true

The CancellationToken is automatically bound as described in issue #14325 (closed) and therefore does not require any other changes and consumers can continue to use the API as normal

@wing328 @mandrean @shibayan @Blackclaws @lucamazzanti

PR checklist

• Read the contribution guidelines.
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• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh

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