Create a negative integration test for malformed gossip certificates.

These are the scenarios that need negative integration tests:
1. Loading gossip certificate that is malformed.
2. Roster contains malformed cert (this may be very hard to test).

These should be tested using a container otter test.

Prereqs:
complete cryptostatic refactoring to seperate Hedera app concepts from key management
https://github.com/hiero-ledger/hiero-consensus-node/issues/15825

Start by checking prerequisite issue #15825 and the existing container otter integration-test entry points; no source file is named here. Cover malformed loaded gossip certificates and investigate whether a roster containing a malformed certificate can be exercised. Done means negative integration coverage exists for the feasible scenarios and passes in the container otter test environment.

Written by the indexing model from the issue text.