Add UI testing workflow for contributor PRs

[AaronMT]

This adds a GitHub Action workflow for running UI smoke tests against contributor forks on Pull Request. It runs against MacOS-latest (here) on Xcode 12.4 (this is configurable). The SmokeXCUITests testplanh is used on an iPhone 11 (also configurable).

Of note there is an issue with a false state check (tbartelmess/analyze-xcoderesults-action#35) on the XCResult parsing step with a Marketplace GitHub Action I am using.

[AaronMT]

@isabelrios Will probably need a force merge because it's trying to run with on: [pull_request] but it doesn't have access to GitHub token yet I guess.

[isabelrios]

@isabelrios Will probably need a force merge because it's trying to run with on: [pull_request] but it doesn't have access to GitHub token yet I guess.

Would that be the cause of this error that can be seen by going to the red check, or that's a different thing?:

pythonLocation: /Users/runner/hostedtoolcache/Python/3.9.5/x64
Analyzing TestResults.xcresult ...
Error: Resource not accessible by integration

[AaronMT]

@isabelrios Will probably need a force merge because it's trying to run with on: [pull_request] but it doesn't have access to GitHub token yet I guess.

Would that be the cause of this error that can be seen by going to the red check, or that's a different thing?:

pythonLocation: /Users/runner/hostedtoolcache/Python/3.9.5/x64
Analyzing TestResults.xcresult ...
Error: Resource not accessible by integration

Yeah I believe so because it can't upload the artifact so it can't parse anything.

[isabelrios]

I'm happy to land this and see how it works. My only concern is the red status report failure if the token is not the solution.. let's have a plan to act in case that's not the cause...

[isabelrios]

Let's try this. Although the result is red, it does not prevent from landing so we can try this out, but I would let the team know so that they don't panic if they see all PRs red temporarly :)