Remove x86intrin.h dependency from fd_util.h #16306

Job	Run time
ledgers / ledger-replay	8m 49s
tests / test (linux_gcc_noarch64)	59s
tests / test (linux_gcc_x86_64)	1m 1s
tests / test (linux_gcc_icelake)	1m 2s
tests / test (linux_clang_x86_64)	1m 3s
tests / test (linux_clang_icelake)	46s
tests / test (native)	1m 2s
ledgers / ledger-coverage	0s
	14m 42s

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