Porting over some Github Actions fixes from the v9 PR

[jamesdaniels]

Cleanup and fixes for the recent webdriver-manager break.

• Only build "on push" on the main branch, this prevent double runs from triggering on PRs
• webdriver-manager defaults to the latest version of chrome, which isn't on github actions yet. This is resulting in the tests failing. Clean up the handling here and pin to the installed version of google-chrome (falling back to latest)
• our build script would recurse... 🤦 don't retrigger build in the generate_test_files.sh, there's also no clean task so dropping that
• use the saucelabs readyfile, since tests are tripping before the socket is established
• upgrade sc again and add OSX support to sauce_connect.sh
• run the local tests first before tripping saucelabs, so it's quicker and easier to tell what tests are red