[Bug] Handle possibility of update-before-start

[Sushisource]

Describe the bug

Because of the fact that we re-order updates to come before other things a-la signals in Core, it's currently possible to handle an update before running the first bit of workflow code if an update comes in same task as start workflow.

We'll likely need to buffer things as we do in other SDKs (in lieu of making some other choice)

Minimal Reproduction

See the test_workflow_update_handlers_unhappy test and discussion here

Environment/Versions

• OS and processor: [e.g. M1 Mac, x86 Windows, Linux]
• Temporal Version: [e.g. 1.14.0?] and/or SDK version
• Are you using Docker or Kubernetes or building Temporal from source?

Additional context

[cretz]

Also, we need to stop reordering of activation jobs inside of Python. Right now this moves signals first and does not account for updates. But we need to make very sure that the Core ordering matches what is already happening (besides update).

[cretz]

.NET equivalent: temporalio/sdk-dotnet#176. We need to make sure we have a test that does a start then update then starts a worker and confirms behavior with dynamically registered handlers.