Add decorator to all "invalid" test cases

[hwwhww]

Fix #3739

I think they all miss the decorator like #3728.

• Check if each case failed at the position we expected.

[fradamt]

Yes, the issue is that with the mainnet preset we would need 0.5M validators in order to have a nonzero consolidation churn limit. For some reason I didn't add the decorators to most of the invalid tests...

[hwwhww]

I verified where these test cases fail:

test case	failed at
test_invalid_source_equals_target	assert consolidation.source_index != consolidation.target_index
test_invalid_exceed_pending_consolidations_limit	assert len(state.pending_consolidations) < PENDING_CONSOLIDATIONS_LIMIT
test_invalid_not_enough_consolidation_churn_available	assert get_consolidation_churn_limit(state) > MIN_ACTIVATION_BALANCE
test_invalid_exited_source	assert source_validator.exit_epoch == FAR_FUTURE_EPOCH
test_invalid_exited_target	assert target_validator.exit_epoch == FAR_FUTURE_EPOCH
test_invalid_inactive_source	assert is_active_validator(source_validator, current_epoch)
test_invalid_inactive_target	assert is_active_validator(target_validator, current_epoch)
test_invalid_no_execution_withdrawal_credential	assert has_execution_withdrawal_credential(source_validator)
test_invalid_different_credentials	assert source_validator.withdrawal_credentials[12:] == target_validator.withdrawal_credentials[12:]
test_invalid_source_signature	assert bls.FastAggregateVerify(pubkeys, signing_root, signed_consolidation.signature)
test_invalid_target_signature	assert bls.FastAggregateVerify(pubkeys, signing_root, signed_consolidation.signature)
test_invalid_before_specified_epoch	assert current_epoch >= consolidation.epoch

Looks all correct now.