Adds LtHash::identity() #10971

Job	Run time
check	2m 12s
test (token/cli, token/program, token/program-2022, associated-token-account/program, instruction...	17m 53s
cargo-test-sbf (token/program)	8m 43s
test (single-pool/cli, single-pool/program)	17m 56s
cargo-test-sbf (instruction-padding/program, token/program-2022, token/program-2022-test)	13m 42s
test (token-upgrade/cli, token-upgrade/program)	16m 10s
cargo-test-sbf (associated-token-account/program, associated-token-account/program-test)	9m 8s
cargo-test-sbf (token-upgrade/program)	7m 52s
cargo-test-sbf (feature-proposal/program)	8m 13s
cargo-test-sbf (governance/addin-mock/program, governance/program)	12m 1s
cargo-test-sbf (memo/program)	7m 14s
cargo-test-sbf (name-service/program)	9m 9s
cargo-test-sbf (stake-pool/program)	11m 20s
cargo-test-sbf (single-pool/program)	9m 0s
	2h 30m 33s

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