Lock free payment validator refactor #1661

Job	Run time
check	2m 50s
rustfmt	10s
audit	29s
clippy	3m 50s
test	10m 25s
integration-test-five-nodes	23m 35s
cross-armv7	1m 9s
cross-aarch64	1m 7s
integration-test-debts	0s
integration-test-althea-payment	0s
integration-test-eth-payments	0s
integration-test-db-migration	0s
integration-test-multi-exit	0s
integration-test-validate-contract	0s
	43m 35s

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