fix(PPDSC-2312): audio player test improvements

[mstuartf]

PPDSC-2312

What

1. Background - why this is needed
   Main issues:

• Player sometimes still in loading state when snapshot taken.
• Arbitrary waits.
• Buffered amount changes, making tests flaky.
• Animations making screenshots inconsistent.
• Time elapsed in autoplay tests not consistent.

3. What did you do
   Fixes (to avoid ignore regions in tests):

• Make sure all players in a test story are loaded before taking the snapshot using oncanplay event.
• Prefetch src for all players so that content is fully buffered. Add separate tests for loading / unbuffered state.
• Disable CSS animations to make screenshots consistent.
• Remove visual tests for autoplay behaviour as this is not necessary. Also remove duplicate autoplay story.
• Remove all arbitrary waits and ignore regions in tests.

5. What does the reviewers should expect
   All AudoPlayer and AudioPlayerComposable visual tests should have no arbitrary waits or ignore regions and should consistently pass.

I have done:

• Written unit tests against changes
• Written functional tests against the component and/or NewsKit site
• Updated relevant documentation

I have tested manually:

• The feature's functionality is working as expected on Chrome, Firefox, Safari and Edge
• The screen reader reads and flows through the elements as expected.
• There are no new errors in the browser console coming from this PR.
• When visual test is not added, it renders correctly on different browsers and mobile viewports (Safari, Firefox, small mobile viewport, tablet)
• The Playground feature is working as expected

Before:

After:

Who should review this PR:

How to test:

[newskit-engineering]

You can preview these changes on:
Documentation Site: http://ncu-newskit-docs.s3-website-eu-west-1.amazonaws.com/ppdsc-2312-audio-player-tests
Storybook: http://ncu-newskit-docs.s3-website-eu-west-1.amazonaws.com/ppdsc-2312-audio-player-tests/storybook