Hashing and prefetching hints for fd_map_chain_para #15956

Job	Run time
ledgers / ledger-replay	8m 54s
firedancer-shredcap / firedancer-testnet-shredcap	5m 50s
tests / test (linux_gcc_noarch64)	58s
tests / test (linux_gcc_x86_64)	7m 26s
tests / test (linux_gcc_icelake)	4m 17s
tests / test (linux_clang_x86_64)	5m 24s
tests / test (linux_clang_icelake)	5m 0s
tests / test (native)	4m 43s
ledgers / ledger-coverage	0s
	42m 32s

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