v1.18: accounts-db: fix 8G+ memory spike during hash calculation (bac… #8105

Job	Run time
check	0s
test	0s
cargo-test-sbf (token/program)	8m 32s
cargo-test-sbf (instruction-padding/program, token/program-2022, token/program-2022-test)	14m 27s
cargo-test-sbf (associated-token-account/program, associated-token-account/program-test)	9m 55s
cargo-test-sbf (token-upgrade/program)	8m 40s
cargo-test-sbf (feature-proposal/program)	8m 41s
cargo-test-sbf (governance/addin-mock/program, governance/program)	12m 40s
cargo-test-sbf (memo/program)	8m 31s
cargo-test-sbf (name-service/program)	8m 45s
cargo-test-sbf (stake-pool/program)	11m 58s
cargo-test-sbf (single-pool/program)	9m 26s
	1h 41m 35s

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