[luke-hill]

Description

This begins to standardise all aspects of the failure results including the messages/exceptions

It also breaks the contract regarding structure of all failed messages including the structure and format of the backtrace/message

The runner now takes 0 liability for the publishing of the test step result message - it takes this entirely from the result classes themselves

Type of change

Please delete options that are not relevant.

• Refactoring (improvements to code design or tooling that don't change behaviour)
• Breaking change (will cause existing functionality to not
  work as expected)

Please add an entry to the relevant section of CHANGELOG.md as part of this pull request.

Note to other contributors

If your change may impact future contributors, explain it here, and remember to update README.md and CONTRIBUTING.md accordingly.

Checklist:

Your PR is ready for review once the following checklist is
complete. You can also add some checks if you want to.

• Tests have been added for any changes to behaviour of the code
• New and existing tests are passing locally and on CI
• bundle exec rubocop reports no offenses
• CHANGELOG.md has been updated