reduce memory copying in tpu-client-next #17303

Job	Run time
check (associated-token-account)	2m 28s
cargo-test-sbf (associated-token-account)	8m 26s
check (feature-proposal)	2m 8s
test_cli (single-pool)	19m 7s
cargo-test-sbf (feature-proposal)	9m 23s
check (instruction-padding)	2m 31s
test_cli (token-2022)	19m 22s
cargo-test-sbf (instruction-padding)	7m 12s
check (memo)	2m 47s
cargo-test-sbf (memo)	6m 30s
check (record)	2m 18s
cargo-test-sbf (record)	7m 27s
check (single-pool)	2m 59s
check (slashing)	2m 40s
cargo-test-sbf (single-pool)	10m 10s
check (stake-pool)	3m 39s
check (token-2022)	4m 0s
cargo-test-sbf (slashing)	14m 51s
cargo-test-sbf (stake-pool)	11m 33s
cargo-test-sbf (token-2022)	7m 52s
	2h 27m 23s

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