Improve logging on Host startup and shutdown host if start up exceeds a threshold

This is follow up item from CRI investigation. When new function runtime `2.0.12888.0` rolled out, customer's application restarted but Jobhost took ~16 minutes to start causing all inflight http requests to timeout.

```
 PreciseTimeStamp Source Summary
2019-12-15 03:18:31.6108487 Host.Startup Host started (984193ms)
```

Logs do not have any details on where the startup got stuck.

Only exception in the logs:

```
The listener for function 'Functions.HopperHubTrigger' was unable to start.
System.OperationCanceledException : The operation was canceled.
at System.Net.Http.HttpClient.HandleFinishSendAsyncError(Exception e,CancellationTokenSource cts)
at async System.Net.Http.HttpClient.FinishSendAsyncUnbuffered(Task`1 sendTask,HttpRequestMessage request,CancellationTokenSource cts,Boolean disposeCts)
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at async Microsoft.WindowsAzure.Storage.Core.Executor.Executor.ExecuteAsyncInternal[T](RESTCommand`1 cmd,IRetryPolicy policy,OperationContext operationContext,CancellationToken token)
```

Start by tracing the Host.Startup logging and the listener startup path described in the issue, including the HopperHubTrigger failure. Review the existing startup duration log and cancellation behavior; done means startup progress is diagnosable in logs and an over-threshold startup causes the host to shut down.

Written by the indexing model from the issue text.