[WEB-3840] remove Cypress in favour of Storybook's test-runner

[jamiehenson]

Jira Ticket Link / Motivation

https://ably.atlassian.net/browse/WEB-3840

Summary of changes

Since the Storybook migration (pre v14), Cypress has been inactive. Upon reflection, now we have Storybook, Cypress seems a somewhat heavy handed approach to testing when we don't need deep integration testing - something like snapshot testing would probably be a good starting point but there wasn't a clear resolution to the conversation.

Thankfully for us, Storybook has options for all of the above. With its own test-runner, we get smoke tests (i.e. does this component render or not) for free for each story, and we have the option of writing more comprehensive testing journeys using Play functions - which given that they're written alongside the stories themselves seems more ergonomic.

This PR brings in test-runner, guts all the cypress stuff, and makes some adjustments to the Github workflows so that the test suite runs on push.

How do you manually test this?

Pull down, run yarn test, Storybook should build and the test suite should run, resulting in a successful set of smoke tests like this

Reviewer Tasks (optional)

Merge/Deploy Checklist

• Written automated tests for implemented features/fixed bugs
• Rebased and squashed commits
• Commits have clear descriptions of their changes
• Checked for any performance regressions

Frontend Checklist

• No frontend changes in this PR
• Added before/after screenshots for changes
• Tested on different platforms/browsers with Browserstack
• Compared with the initial design / our brand guidelines
• Checked the code for accessibility issues (VoiceOver User Guide)?

[jamiehenson]

This aligns with Node 16, which is the minimum requirement across our other apps

[kennethkalmer]

This looks great @jamiehenson, thanks!

Just an aside, the tests for the Status component is definitely flaky and we will get false negatives. This is because it goes from a loading state to whatever the story dictates, and depending on the time of the snapshot it might still be doing its animated pulse rather than rendering the status colour. I don't think it should block us for now, just as long as we're aware :)

[aralovelace]

cant wait for this

[jamiehenson]

@kennethkalmer I removed the "Live" story on Status which was causing some flakiness, but the others seemed to be well stubbed so not expecting further flakiness - might not have gone far enough though