Properly store answer state after initial attempt for exercises

[rtibbles]

Summary

• Answer state in the frontend was being erroneously overwritten, meaning the appropriate corrected state was not being shown to the user
• This fixes that by not storing these fields into the vuex store when the attempt already exists there, if the 'replace' flag is not specified.

References

Fixes #8606

Reviewer guidance

Answer an exercise question incorrectly - now get it right - does it show as 'corrected' (small black dot) rather than 'correct' (big green tick/check mark)?

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[pcenov]

Tested and confirmed that the issue is fixed in this build.

[radinamatic]

corrected_correctly in now correct! 🎉

[radinamatic]

All correct! 💯