Slashing delegation integration test

[philipjames44]

E.g. https://github.com/Gravity-Bridge/Gravity-Bridge/blob/main/orchestrator/test_runner/src/slashing_delegation.rs

Note this is important as a 'bug caused delegations and delegation withdraws to fail when a validator was slashed in a specific way,' we should verify this bug doesn't exist in our gravity module before we have slashing.