[Feature Request] Add Task Queue Priority and Fairness sample

Is your feature request related to a problem? Please describe.

There is documentation for Task Queue Priority and Fairness, but I could not find a Go sample that demonstrates how to use it.

Describe the solution you'd like

Add a simple Go sample for Task Queue Priority and Fairness.

The sample should show how users can set PriorityKey, FairnessKey, and FairnessWeight on Activity options. It can use a small multi-tenant workload where urgent work runs first and tenants share dispatch fairly within the same priority level.

Additional context

Docs : https://docs.temporal.io/develop/task-queue-priority-fairness

Start by reviewing the Task Queue Priority and Fairness documentation and locating existing Go samples in this repository. Add a small multi-tenant workload demonstrating Activity options with PriorityKey, FairnessKey, and FairnessWeight, then run the relevant sample checks to confirm urgent work is prioritized and dispatch is fair within a priority level.