validation: followups for de-duplication of packages

Summary:

- Add a test for packages with a mix of duplicate/different witness/new parents
- Fix issue with not notifying CValidationInterface when there's a partial submission due to fail-fast

This completes backport of core#23804.
For previous diffs, see D12913.

The test has been adapted and renamed to match our codebase.

Depends on D16387.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D16389