Decouple TestCaseResult from formatting implementations

[lvukosavljevic-rivianvw]

I think it would be useful if the formatter was decoupled into an interface. So a new command line option would be --format. The options could be:

• xprin - Current default formatter
• yaml - Great for machine parsable outputs and dyffing in e2e tests. Easier to read and change the e2e tests
• junit - Great for pipelines. Both GitLab support rendering this natively. Github can also render it with the use of an action