A0-4563: Added unit test for censorship resistance in Extender

[Marcin-Radecki]

Introduced 2 UTs, similar to existing ones, but with prepared DAG that contains non-direct parents. It turns out that current testing code almost support non-direct parents, as ReconstructedUnit control hash is created based on the parents injected by the test, except one method random_unit_with_parents that assumed each parent round is the same.

Currently, those tests are disabled since they (expectedly) panic at

units are added in order
thread 'extension::extender::test::given_minimal_dag_with_orphaned_node_when_producing_batches_have_correct_length' panicked at consensus/src/extension/election.rs:56:42:

This PR should not contain any changes to the production code.

[github-actions]

Please make sure the following happened

• Appropriate tests created
• Infrastructure updated accordingly
• Updated existing documentation
• New documentation created
• Version bumped if breaking changes

[timorleph]

Strict TDD in ABFT, I've never thought I would see the day... <3 (;_;) <3