Update solidity to 0.8.21 #1410

Job	Run time
check	28s
clippy	39s
audit	17s
test	3m 9s
rustfmt	7s
cross-mips	54s
cross-mips64	38s
cross-armv7	44s
cross-aarch64	41s
cross-mips64el	1m 1s
cross-mipsel	44s
integration-test-five-nodes	23m 2s
legacy_integration-test	23m 14s
legacy_integration-test-with-backcompat	19m 21s
integration-test-althea-payment	22m 34s
integration-test-debts	29m 35s
integration-test-eth-payments	19m 26s
integration-test-multi-exit	23m 17s
	2h 49m 51s

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