Update exit list signing infra for contract based exits #2030

Job	Run time
check	23s
audit	10s
clippy	24s
test	5m 17s
rustfmt	3s
integration-test-althea-payment	10m 52s
integration-test-db-migration	6m 26s
integration-test-debts	10m 4s
integration-test-eth-payments	11m 35s
integration-test-five-nodes	7m 1s
integration-test-multi-exit	7m 50s
integration-test-validate-contract	6m 31s
cross-aarch64	0s
cross-armv7	0s
	1h 6m 36s

Provide feedback