Add ExecutionStatusMarkedAsFailed

[AgnesToulet]

What?

This PR adds a new status to mark the end of a test: ExecutionStatusMarkedAsFailed that should be set when execution.test.fail() is called in the test. This is only creating the status so we can use it in the test-coordinator (see PR)

Then, we'll be able to use it in another PR but this PR requires the changes in the test-coordinator to be merged and deployed first so it knows how to handle this new status.

Why?

This will allow to return a better status in the Cloud. For now, the associated k6-cloud-testcoordinator PR uses this to return cloudapi.RunStatusAbortedUser (as if the test was interrupted with abort) but we could work with the cloud team next to introduce a new status.

Note, that an alternative to this if we only want to focus on the short-term solution would be to use ExecutionStatusInterrupted instead. Then, we wouldn't need the PR in k6-cloud-testcoordinator to return cloudapi.RunStatusAbortedUser (as it's already the case when ExecutionStatusInterrupted is received).

Checklist

• I have performed a self-review of my code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have added tests for my changes.
• I have run linter and tests locally (make check) and all pass.

Checklist: Documentation (only for k6 maintainers and if relevant)

Please do not merge this PR until the following items are filled out.

• I have added the correct milestone and labels to the PR.
• I have updated the release notes: link
• I have updated or added an issue to the k6-documentation: grafana/k6-docs#NUMBER if applicable
• I have updated or added an issue to the TypeScript definitions: grafana/k6-DefinitelyTyped#NUMBER if applicable

Related PR(s)/Issue(s)

Part of https://github.com/grafana/k6-cloud/issues/4022