Updating Sauce Labs tunnel instructions

[daynew]

I wanted to setup Sauce Labs tunnel for the first time on my laptop but I ran into problems because the commands didn't match what we have documented. It looks like the sc Sauce Connect Proxy CLI has been updated to require more arguments:

• region e.g. "us-west"
• tunnel-name e.g. "dayne_localhost"
  • The important part of the tunnel name is that it has to matches what you use when running sc run --tunnel-name

This PR:

• Creates a new config value CDO.saucelabs_tunnel_name so the UI tests can find the tunnel sc has started.
• Update the README file related to running the Sauce Labs tunnel.

An alternative to creating the config property CDO.saucelabs_tunnel_name is to set CDO.circle_run_identifier in your locals.yml. However, I think creating a new config value is more readable.

Testing story

• Started the tunnel and successfully ran UI tests.

PR Checklist:

• Tests provide adequate coverage
• Privacy and Security impacts have been assessed
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked

[Hamms]

One comment requested, but otherwise this looks good to me! I'm looking forward to not getting confused about the discrepancy regarding tunnel names between official docs and our docs the next time I need to use local sauceconnect; thank you! 😄

[breville]

Thanks for taking the time to do this!