Merge branch 'alex/add-idkg-retain-active-key-unit-tests' into 'master'

test(crypto): CRP-1473 add more tests for `idkg_retain_active_keys`

Adds the following tests:
```
should_fail_on_serialization_error_from_pks_during_retention
should_fail_if_oldest_pk_not_found_during_retention
should_fail_if_oldest_pk_not_found_during_would_retain_modify_pks
should_fail_if_pk_proto_algorithm_id_unsupported
should_fail_if_failed_deserialize_pk_proto
should_fail_if_sks_retain_fails
should_fail_if_csks_retain_fails
``` 

See merge request dfinity-lab/public/ic!17536