ExtensionData in OrchestrationInstanceEx can share between OrchestrationDispatcherMiddleware but not ActivityDispatcherMiddleware

According #503, I think we can share session data between Orchestration and Activity. But my test did not meet expectations. My expected result is `customInstance` in every middle can share the `Dic` data. The test project is [here ](https://github.com/ChenglongLiu/durabletaskTest/tree/master/UseAzuriteTest/SessionDataTest).

`

taskHub.AddOrchestrationDispatcherMiddleware(async (context, next) =>
{
OrchestrationRuntimeState runtimeState = context.GetProperty();
var customInstance = OrchestrationInstanceEx.Initialize(runtimeState);
customInstance.Dic["a"] = "a";
customInstance.Dic["b"] = "b";
customInstance.Dic["c"] = "c";
context.SetProperty(customInstance);
await next();
});

taskHub.AddOrchestrationDispatcherMiddleware(async (context, next) =>
{
var customInstance = OrchestrationInstanceEx.Get(context.GetProperty());
context.SetProperty(customInstance);

//Dic data can get here. But missed in HelloOrchestration context and ActivityDispatcherMiddleware

await next();
});

taskHub.AddActivityDispatcherMiddleware(async (context, next) =>
{
var customInstance = OrchestrationInstanceEx.Get(context.GetProperty());
context.SetProperty(customInstance);

//Dic data can missed here

await next();
});
`