Fix acceptance reports path, how to get the latest merged PR and avoid running tests multiple times

[fab-10]

PR description

Follow up to #7141, to fix the acceptance test path, and adjust the query to correctly get the last PR merged by time, instead of by number. There is also a fix to prevent recursively adding previous downloaded test results into new reports, with the result of running tests multiple times.

Fixed Issue(s)

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• [ ] Checked out our contribution guidelines?
• [ ] Considered documentation and added the doc-change-required label to this PR if updates are required.
• [ ] Considered the changelog and included an update if required.
• [ ] For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• [ ] unit tests: ./gradlew build
• [ ] acceptance tests: ./gradlew acceptanceTest
• [ ] integration tests: ./gradlew integrationTest
• [ ] reference tests: ./gradlew ethereum:referenceTests:referenceTests