Minor Optimizations

[siri-varma]

Made the executor code more aligned with the current durable worker task design

Issue describing the changes in this PR

resolves #issue_for_this_pr

Pull request checklist

• [X ] My changes do not require documentation changes
  • [X ] Otherwise: Documentation issue linked to PR
• [X ] My changes are added to the CHANGELOG.md
• [ X] I have added all required tests (Unit tests, E2E tests)

Additional information

Additional PR information

[siri-varma]

@cicoyle , @salaboy Please take a look at this small PR. The design here is more aligned with what the current durable task is doing.

If anything is provided, the durable sdk does not manage it. That is how the GRPC channel is designed today. So even in our case, if the executor service is provided, the durable task will not manage it.