optimize AccountIndexIterator to reuse last loaded bin-map item range #18335

Job	Run time
cargo-test-sbf (associated-token-account)	7m 27s
check (associated-token-account)	1m 50s
cargo-test-sbf (feature-proposal)	5m 53s
test_cli (single-pool)	16m 50s
cargo-test-sbf (instruction-padding)	7m 45s
check (feature-proposal)	1m 47s
test_cli (token-2022)	15m 46s
cargo-test-sbf (memo)	5m 21s
check (instruction-padding)	2m 39s
cargo-test-sbf (record)	7m 27s
check (memo)	2m 50s
cargo-test-sbf (single-pool)	7m 39s
cargo-test-sbf (slashing)	12m 52s
check (record)	1m 36s
cargo-test-sbf (stake-pool)	10m 56s
check (single-pool)	2m 11s
cargo-test-sbf (token-2022)	6m 31s
check (slashing)	1m 15s
check (stake-pool)	3m 29s
check (token-2022)	3m 33s
	2h 5m 37s

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