Add proper unit / integration tests for parentclosepolicy workflow

[mastermanu]

Context: We had a nil ref bug in the workflow where the activity was not passing in a context, which meant that this Workflow was always failing. Although we fixed the bug, there is a lack of unit/integration testing that should have protected us against this (it was caught by stress testing, but that is far too late to catch such a basic issue)

[vaibhavyadav-dev]

can I take this one @samarabbas ?

[endo0911engineer]

https://github.com/temporalio/sdk-go/pull/2023

Hi, I have created a PR that addresses this issue. The PR adds a test for NilContextWorkflow to ensure safety when executing activities with a nil context.

Thanks for your patience!