TINYMCE-14759: Handle hook failures and stray promise rejections

[TheSpyder]

Related Ticket: TINYMCE-14759

Description of Changes:

• Rejected promises in before and after hooks no longer cause the entire test run to crash
• The front-end will now attempt to assign stray promise rejections to the test that created them instead of swallowing the failure

Pre-checks:

• Changelog entry added
• package.json versions have not been changed (done by Lerna on release)
• Tests have been added (if applicable)

Before merging:

• Ensure internal dependencies are on appropriate versions
  • For stable releases, all dependencies must be stable
  • For release candidates, all dependencies must be release candidates or stable