test(dev-server): support UI port

What was changed

Added ui_port parameter to WorkflowEnvironment.start_local() method to allow users to customize the UI port when starting a local Temporal dev server environment.

Why?

This feature allows users to specify a custom UI port when starting the dev server

Checklist

1. Closes #748

2. How was this tested:

   • Test verifies that the server starts successfully with the configured UI port

3. Any docs updates needed?

   • Parameter is already documented in the docstring of start_local() method
   • No additional README or external docs changes required as this is an internal testing feature