This commit partially reverts #868 to restore the intrinsics to their
original implementation to avoid breaking changes. This is done while
rust-lang/rust#73166 is running through crater, and should unblock
rust-lang/rust#74482.
* Update Intel intrinsics definitions with the latest version
* Update _mm256_extract_epi{8,16} to match latest definition
* Fix _mm_extract_epi16 sign extension
Fixes#867